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Revision 1.63 by root, Mon Mar 4 10:28:38 2019 UTC

1NAME 1NAME
2 IO::AIO - Asynchronous Input/Output 2 IO::AIO - Asynchronous/Advanced Input/Output
3 3
4SYNOPSIS 4SYNOPSIS
5 use IO::AIO; 5 use IO::AIO;
6 6
7 aio_open "/etc/passwd", O_RDONLY, 0, sub { 7 aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
8 my $fh = shift 8 my $fh = shift
9 or die "/etc/passwd: $!"; 9 or die "/etc/passwd: $!";
10 ... 10 ...
11 }; 11 };
12 12
… …
24 $req->cancel; # cancel request if still in queue 24 $req->cancel; # cancel request if still in queue
25 25
26 my $grp = aio_group sub { print "all stats done\n" }; 26 my $grp = aio_group sub { print "all stats done\n" };
27 add $grp aio_stat "..." for ...; 27 add $grp aio_stat "..." for ...;
28 28
29 # AnyEvent integration
30 open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";
31 my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });
32
33 # Event integration
34 Event->io (fd => IO::AIO::poll_fileno,
35 poll => 'r',
36 cb => \&IO::AIO::poll_cb);
37
38 # Glib/Gtk2 integration
39 add_watch Glib::IO IO::AIO::poll_fileno,
40 in => sub { IO::AIO::poll_cb; 1 };
41
42 # Tk integration
43 Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
44 readable => \&IO::AIO::poll_cb);
45
46 # Danga::Socket integration
47 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
48 \&IO::AIO::poll_cb);
49
50DESCRIPTION 29DESCRIPTION
51 This module implements asynchronous I/O using whatever means your 30 This module implements asynchronous I/O using whatever means your
52 operating system supports. 31 operating system supports. It is implemented as an interface to "libeio"
32 (<http://software.schmorp.de/pkg/libeio.html>).
53 33
54 Asynchronous means that operations that can normally block your program 34 Asynchronous means that operations that can normally block your program
55 (e.g. reading from disk) will be done asynchronously: the operation will 35 (e.g. reading from disk) will be done asynchronously: the operation will
56 still block, but you can do something else in the meantime. This is 36 still block, but you can do something else in the meantime. This is
57 extremely useful for programs that need to stay interactive even when 37 extremely useful for programs that need to stay interactive even when
… …
61 faster on a RAID volume or over NFS when you do a number of stat 41 faster on a RAID volume or over NFS when you do a number of stat
62 operations concurrently. 42 operations concurrently.
63 43
64 While most of this works on all types of file descriptors (for example 44 While most of this works on all types of file descriptors (for example
65 sockets), using these functions on file descriptors that support 45 sockets), using these functions on file descriptors that support
66 nonblocking operation (again, sockets, pipes etc.) is very inefficient 46 nonblocking operation (again, sockets, pipes etc.) is very inefficient.
67 or might not work (aio_read fails on sockets/pipes/fifos). Use an event
68 loop for that (such as the Event module): IO::AIO will naturally fit 47 Use an event loop for that (such as the EV module): IO::AIO will
69 into such an event loop itself. 48 naturally fit into such an event loop itself.
70 49
71 In this version, a number of threads are started that execute your 50 In this version, a number of threads are started that execute your
72 requests and signal their completion. You don't need thread support in 51 requests and signal their completion. You don't need thread support in
73 perl, and the threads created by this module will not be visible to 52 perl, and the threads created by this module will not be visible to
74 perl. In the future, this module might make use of the native aio 53 perl. In the future, this module might make use of the native aio
… …
76 not well-supported or restricted (GNU/Linux doesn't allow them on normal 55 not well-supported or restricted (GNU/Linux doesn't allow them on normal
77 files currently, for example), and they would only support aio_read and 56 files currently, for example), and they would only support aio_read and
78 aio_write, so the remaining functionality would have to be implemented 57 aio_write, so the remaining functionality would have to be implemented
79 using threads anyway. 58 using threads anyway.
80 59
60 In addition to asynchronous I/O, this module also exports some rather
61 arcane interfaces, such as "madvise" or linux's "splice" system call,
62 which is why the "A" in "AIO" can also mean *advanced*.
63
81 Although the module will work with in the presence of other (Perl-) 64 Although the module will work in the presence of other (Perl-) threads,
82 threads, it is currently not reentrant in any way, so use appropriate 65 it is currently not reentrant in any way, so use appropriate locking
83 locking yourself, always call "poll_cb" from within the same thread, or 66 yourself, always call "poll_cb" from within the same thread, or never
84 never call "poll_cb" (or other "aio_" functions) recursively. 67 call "poll_cb" (or other "aio_" functions) recursively.
85 68
86 EXAMPLE 69 EXAMPLE
87 This is a simple example that uses the Event module and loads 70 This is a simple example that uses the EV module and loads /etc/passwd
88 /etc/passwd asynchronously: 71 asynchronously:
89 72
90 use Fcntl;
91 use Event; 73 use EV;
92 use IO::AIO; 74 use IO::AIO;
93 75
94 # register the IO::AIO callback with Event 76 # register the IO::AIO callback with EV
95 Event->io (fd => IO::AIO::poll_fileno, 77 my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
96 poll => 'r',
97 cb => \&IO::AIO::poll_cb);
98 78
99 # queue the request to open /etc/passwd 79 # queue the request to open /etc/passwd
100 aio_open "/etc/passwd", O_RDONLY, 0, sub { 80 aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
101 my $fh = shift 81 my $fh = shift
102 or die "error while opening: $!"; 82 or die "error while opening: $!";
103 83
104 # stat'ing filehandles is generally non-blocking 84 # stat'ing filehandles is generally non-blocking
105 my $size = -s $fh; 85 my $size = -s $fh;
… …
114 94
115 # file contents now in $contents 95 # file contents now in $contents
116 print $contents; 96 print $contents;
117 97
118 # exit event loop and program 98 # exit event loop and program
119 Event::unloop; 99 EV::break;
120 }; 100 };
121 }; 101 };
122 102
123 # possibly queue up other requests, or open GUI windows, 103 # possibly queue up other requests, or open GUI windows,
124 # check for sockets etc. etc. 104 # check for sockets etc. etc.
125 105
126 # process events as long as there are some: 106 # process events as long as there are some:
127 Event::loop; 107 EV::run;
128 108
129REQUEST ANATOMY AND LIFETIME 109REQUEST ANATOMY AND LIFETIME
130 Every "aio_*" function creates a request. which is a C data structure 110 Every "aio_*" function creates a request. which is a C data structure
131 not directly visible to Perl. 111 not directly visible to Perl.
132 112
… …
168 anymore (except possibly for the Perl object, but its connection to 148 anymore (except possibly for the Perl object, but its connection to
169 the actual aio request is severed and calling its methods will 149 the actual aio request is severed and calling its methods will
170 either do nothing or result in a runtime error). 150 either do nothing or result in a runtime error).
171 151
172FUNCTIONS 152FUNCTIONS
173 AIO REQUEST FUNCTIONS 153 QUICK OVERVIEW
154 This section simply lists the prototypes most of the functions for quick
155 reference. See the following sections for function-by-function
156 documentation.
157
158 aio_wd $pathname, $callback->($wd)
159 aio_open $pathname, $flags, $mode, $callback->($fh)
160 aio_close $fh, $callback->($status)
161 aio_seek $fh,$offset,$whence, $callback->($offs)
162 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
163 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
164 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
165 aio_readahead $fh,$offset,$length, $callback->($retval)
166 aio_stat $fh_or_path, $callback->($status)
167 aio_lstat $fh, $callback->($status)
168 aio_statvfs $fh_or_path, $callback->($statvfs)
169 aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
170 aio_chown $fh_or_path, $uid, $gid, $callback->($status)
171 aio_chmod $fh_or_path, $mode, $callback->($status)
172 aio_truncate $fh_or_path, $offset, $callback->($status)
173 aio_allocate $fh, $mode, $offset, $len, $callback->($status)
174 aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
175 aio_unlink $pathname, $callback->($status)
176 aio_mknod $pathname, $mode, $dev, $callback->($status)
177 aio_link $srcpath, $dstpath, $callback->($status)
178 aio_symlink $srcpath, $dstpath, $callback->($status)
179 aio_readlink $pathname, $callback->($link)
180 aio_realpath $pathname, $callback->($path)
181 aio_rename $srcpath, $dstpath, $callback->($status)
182 aio_rename2 $srcpath, $dstpath, $flags, $callback->($status)
183 aio_mkdir $pathname, $mode, $callback->($status)
184 aio_rmdir $pathname, $callback->($status)
185 aio_readdir $pathname, $callback->($entries)
186 aio_readdirx $pathname, $flags, $callback->($entries, $flags)
187 IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
188 IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN
189 aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
190 aio_load $pathname, $data, $callback->($status)
191 aio_copy $srcpath, $dstpath, $callback->($status)
192 aio_move $srcpath, $dstpath, $callback->($status)
193 aio_rmtree $pathname, $callback->($status)
194 aio_fcntl $fh, $cmd, $arg, $callback->($status)
195 aio_ioctl $fh, $request, $buf, $callback->($status)
196 aio_sync $callback->($status)
197 aio_syncfs $fh, $callback->($status)
198 aio_fsync $fh, $callback->($status)
199 aio_fdatasync $fh, $callback->($status)
200 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
201 aio_pathsync $pathname, $callback->($status)
202 aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC, $callback->($status)
203 aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
204 aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
205 aio_mlockall $flags, $callback->($status)
206 aio_group $callback->(...)
207 aio_nop $callback->()
208
209 $prev_pri = aioreq_pri [$pri]
210 aioreq_nice $pri_adjust
211
212 IO::AIO::poll_wait
213 IO::AIO::poll_cb
214 IO::AIO::poll
215 IO::AIO::flush
216 IO::AIO::max_poll_reqs $nreqs
217 IO::AIO::max_poll_time $seconds
218 IO::AIO::min_parallel $nthreads
219 IO::AIO::max_parallel $nthreads
220 IO::AIO::max_idle $nthreads
221 IO::AIO::idle_timeout $seconds
222 IO::AIO::max_outstanding $maxreqs
223 IO::AIO::nreqs
224 IO::AIO::nready
225 IO::AIO::npending
226 $nfd = IO::AIO::get_fdlimit [EXPERIMENTAL]
227 IO::AIO::min_fdlimit $nfd [EXPERIMENTAL]
228
229 IO::AIO::sendfile $ofh, $ifh, $offset, $count
230 IO::AIO::fadvise $fh, $offset, $len, $advice
231 IO::AIO::mmap $scalar, $length, $prot, $flags[, $fh[, $offset]]
232 IO::AIO::munmap $scalar
233 IO::AIO::mremap $scalar, $new_length, $flags[, $new_address]
234 IO::AIO::madvise $scalar, $offset, $length, $advice
235 IO::AIO::mprotect $scalar, $offset, $length, $protect
236 IO::AIO::munlock $scalar, $offset = 0, $length = undef
237 IO::AIO::munlockall
238
239 API NOTES
174 All the "aio_*" calls are more or less thin wrappers around the syscall 240 All the "aio_*" calls are more or less thin wrappers around the syscall
175 with the same name (sans "aio_"). The arguments are similar or 241 with the same name (sans "aio_"). The arguments are similar or
176 identical, and they all accept an additional (and optional) $callback 242 identical, and they all accept an additional (and optional) $callback
177 argument which must be a code reference. This code reference will get 243 argument which must be a code reference. This code reference will be
178 called with the syscall return code (e.g. most syscalls return -1 on 244 called after the syscall has been executed in an asynchronous fashion.
179 error, unlike perl, which usually delivers "false") as it's sole 245 The results of the request will be passed as arguments to the callback
180 argument when the given syscall has been executed asynchronously. 246 (and, if an error occured, in $!) - for most requests the syscall return
247 code (e.g. most syscalls return -1 on error, unlike perl, which usually
248 delivers "false").
249
250 Some requests (such as "aio_readdir") pass the actual results and
251 communicate failures by passing "undef".
181 252
182 All functions expecting a filehandle keep a copy of the filehandle 253 All functions expecting a filehandle keep a copy of the filehandle
183 internally until the request has finished. 254 internally until the request has finished.
184 255
185 All functions return request objects of type IO::AIO::REQ that allow 256 All functions return request objects of type IO::AIO::REQ that allow
186 further manipulation of those requests while they are in-flight. 257 further manipulation of those requests while they are in-flight.
187 258
188 The pathnames you pass to these routines *must* be absolute and encoded 259 The pathnames you pass to these routines *should* be absolute. The
189 as octets. The reason for the former is that at the time the request is 260 reason for this is that at the time the request is being executed, the
190 being executed, the current working directory could have changed. 261 current working directory could have changed. Alternatively, you can
191 Alternatively, you can make sure that you never change the current 262 make sure that you never change the current working directory anywhere
192 working directory anywhere in the program and then use relative paths. 263 in the program and then use relative paths. You can also take advantage
264 of IO::AIOs working directory abstraction, that lets you specify paths
265 relative to some previously-opened "working directory object" - see the
266 description of the "IO::AIO::WD" class later in this document.
193 267
194 To encode pathnames as octets, either make sure you either: a) always 268 To encode pathnames as octets, either make sure you either: a) always
195 pass in filenames you got from outside (command line, readdir etc.) 269 pass in filenames you got from outside (command line, readdir etc.)
196 without tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module 270 without tinkering, b) are in your native filesystem encoding, c) use the
197 and encode your pathnames to the locale (or other) encoding in effect in 271 Encode module and encode your pathnames to the locale (or other)
198 the user environment, d) use Glib::filename_from_unicode on unicode 272 encoding in effect in the user environment, d) use
199 filenames or e) use something else to ensure your scalar has the correct 273 Glib::filename_from_unicode on unicode filenames or e) use something
200 contents. 274 else to ensure your scalar has the correct contents.
201 275
202 This works, btw. independent of the internal UTF-8 bit, which IO::AIO 276 This works, btw. independent of the internal UTF-8 bit, which IO::AIO
203 handles correctly wether it is set or not. 277 handles correctly whether it is set or not.
204 278
279 AIO REQUEST FUNCTIONS
205 $prev_pri = aioreq_pri [$pri] 280 $prev_pri = aioreq_pri [$pri]
206 Returns the priority value that would be used for the next request 281 Returns the priority value that would be used for the next request
207 and, if $pri is given, sets the priority for the next aio request. 282 and, if $pri is given, sets the priority for the next aio request.
208 283
209 The default priority is 0, the minimum and maximum priorities are -4 284 The default priority is 0, the minimum and maximum priorities are -4
… …
231 Similar to "aioreq_pri", but subtracts the given value from the 306 Similar to "aioreq_pri", but subtracts the given value from the
232 current priority, so the effect is cumulative. 307 current priority, so the effect is cumulative.
233 308
234 aio_open $pathname, $flags, $mode, $callback->($fh) 309 aio_open $pathname, $flags, $mode, $callback->($fh)
235 Asynchronously open or create a file and call the callback with a 310 Asynchronously open or create a file and call the callback with a
236 newly created filehandle for the file. 311 newly created filehandle for the file (or "undef" in case of an
312 error).
237 313
238 The pathname passed to "aio_open" must be absolute. See API NOTES, 314 The pathname passed to "aio_open" must be absolute. See API NOTES,
239 above, for an explanation. 315 above, for an explanation.
240 316
241 The $flags argument is a bitmask. See the "Fcntl" module for a list. 317 The $flags argument is a bitmask. See the "Fcntl" module for a list.
242 They are the same as used by "sysopen". 318 They are the same as used by "sysopen".
243 319
244 Likewise, $mode specifies the mode of the newly created file, if it 320 Likewise, $mode specifies the mode of the newly created file, if it
245 didn't exist and "O_CREAT" has been given, just like perl's 321 didn't exist and "O_CREAT" has been given, just like perl's
246 "sysopen", except that it is mandatory (i.e. use 0 if you don't 322 "sysopen", except that it is mandatory (i.e. use 0 if you don't
247 create new files, and 0666 or 0777 if you do). 323 create new files, and 0666 or 0777 if you do). Note that the $mode
324 will be modified by the umask in effect then the request is being
325 executed, so better never change the umask.
248 326
249 Example: 327 Example:
250 328
251 aio_open "/etc/passwd", O_RDONLY, 0, sub { 329 aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
252 if ($_[0]) { 330 if ($_[0]) {
253 print "open successful, fh is $_[0]\n"; 331 print "open successful, fh is $_[0]\n";
254 ... 332 ...
255 } else { 333 } else {
256 die "open failed: $!\n"; 334 die "open failed: $!\n";
257 } 335 }
258 }; 336 };
259 337
338 In addition to all the common open modes/flags ("O_RDONLY",
339 "O_WRONLY", "O_RDWR", "O_CREAT", "O_TRUNC", "O_EXCL" and
340 "O_APPEND"), the following POSIX and non-POSIX constants are
341 available (missing ones on your system are, as usual, 0):
342
343 "O_ASYNC", "O_DIRECT", "O_NOATIME", "O_CLOEXEC", "O_NOCTTY",
344 "O_NOFOLLOW", "O_NONBLOCK", "O_EXEC", "O_SEARCH", "O_DIRECTORY",
345 "O_DSYNC", "O_RSYNC", "O_SYNC", "O_PATH", "O_TMPFILE", "O_TTY_INIT"
346 and "O_ACCMODE".
347
260 aio_close $fh, $callback->($status) 348 aio_close $fh, $callback->($status)
261 Asynchronously close a file and call the callback with the result 349 Asynchronously close a file and call the callback with the result
262 code. *WARNING:* although accepted, you should not pass in a perl 350 code.
263 filehandle here, as perl will likely close the file descriptor
264 another time when the filehandle is destroyed. Normally, you can
265 safely call perls "close" or just let filehandles go out of scope.
266 351
267 This is supposed to be a bug in the API, so that might change. It's 352 Unfortunately, you can't do this to perl. Perl *insists* very
268 therefore best to avoid this function. 353 strongly on closing the file descriptor associated with the
354 filehandle itself.
355
356 Therefore, "aio_close" will not close the filehandle - instead it
357 will use dup2 to overwrite the file descriptor with the write-end of
358 a pipe (the pipe fd will be created on demand and will be cached).
359
360 Or in other words: the file descriptor will be closed, but it will
361 not be free for reuse until the perl filehandle is closed.
362
363 aio_seek $fh, $offset, $whence, $callback->($offs)
364 Seeks the filehandle to the new $offset, similarly to perl's
365 "sysseek". The $whence can use the traditional values (0 for
366 "IO::AIO::SEEK_SET", 1 for "IO::AIO::SEEK_CUR" or 2 for
367 "IO::AIO::SEEK_END").
368
369 The resulting absolute offset will be passed to the callback, or -1
370 in case of an error.
371
372 In theory, the $whence constants could be different than the
373 corresponding values from Fcntl, but perl guarantees they are the
374 same, so don't panic.
375
376 As a GNU/Linux (and maybe Solaris) extension, also the constants
377 "IO::AIO::SEEK_DATA" and "IO::AIO::SEEK_HOLE" are available, if they
378 could be found. No guarantees about suitability for use in
379 "aio_seek" or Perl's "sysseek" can be made though, although I would
380 naively assume they "just work".
269 381
270 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval) 382 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
271 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval) 383 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
272 Reads or writes "length" bytes from the specified "fh" and "offset" 384 Reads or writes $length bytes from or to the specified $fh and
273 into the scalar given by "data" and offset "dataoffset" and calls 385 $offset into the scalar given by $data and offset $dataoffset and
274 the callback without the actual number of bytes read (or -1 on 386 calls the callback with the actual number of bytes transferred (or
275 error, just like the syscall). 387 -1 on error, just like the syscall).
388
389 "aio_read" will, like "sysread", shrink or grow the $data scalar to
390 offset plus the actual number of bytes read.
391
392 If $offset is undefined, then the current file descriptor offset
393 will be used (and updated), otherwise the file descriptor offset
394 will not be changed by these calls.
395
396 If $length is undefined in "aio_write", use the remaining length of
397 $data.
398
399 If $dataoffset is less than zero, it will be counted from the end of
400 $data.
276 401
277 The $data scalar *MUST NOT* be modified in any way while the request 402 The $data scalar *MUST NOT* be modified in any way while the request
278 is outstanding. Modifying it can result in segfaults or WW3 (if the 403 is outstanding. Modifying it can result in segfaults or World War
279 necessary/optional hardware is installed). 404 III (if the necessary/optional hardware is installed).
280 405
281 Example: Read 15 bytes at offset 7 into scalar $buffer, starting at 406 Example: Read 15 bytes at offset 7 into scalar $buffer, starting at
282 offset 0 within the scalar: 407 offset 0 within the scalar:
283 408
284 aio_read $fh, 7, 15, $buffer, 0, sub { 409 aio_read $fh, 7, 15, $buffer, 0, sub {
… …
289 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval) 414 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
290 Tries to copy $length bytes from $in_fh to $out_fh. It starts 415 Tries to copy $length bytes from $in_fh to $out_fh. It starts
291 reading at byte offset $in_offset, and starts writing at the current 416 reading at byte offset $in_offset, and starts writing at the current
292 file offset of $out_fh. Because of that, it is not safe to issue 417 file offset of $out_fh. Because of that, it is not safe to issue
293 more than one "aio_sendfile" per $out_fh, as they will interfere 418 more than one "aio_sendfile" per $out_fh, as they will interfere
294 with each other. 419 with each other. The same $in_fh works fine though, as this function
420 does not move or use the file offset of $in_fh.
295 421
422 Please note that "aio_sendfile" can read more bytes from $in_fh than
423 are written, and there is no way to find out how many more bytes
424 have been read from "aio_sendfile" alone, as "aio_sendfile" only
425 provides the number of bytes written to $out_fh. Only if the result
426 value equals $length one can assume that $length bytes have been
427 read.
428
429 Unlike with other "aio_" functions, it makes a lot of sense to use
430 "aio_sendfile" on non-blocking sockets, as long as one end
431 (typically the $in_fh) is a file - the file I/O will then be
432 asynchronous, while the socket I/O will be non-blocking. Note,
433 however, that you can run into a trap where "aio_sendfile" reads
434 some data with readahead, then fails to write all data, and when the
435 socket is ready the next time, the data in the cache is already
436 lost, forcing "aio_sendfile" to again hit the disk. Explicit
437 "aio_read" + "aio_write" let's you better control resource usage.
438
296 This call tries to make use of a native "sendfile" syscall to 439 This call tries to make use of a native "sendfile"-like syscall to
297 provide zero-copy operation. For this to work, $out_fh should refer 440 provide zero-copy operation. For this to work, $out_fh should refer
298 to a socket, and $in_fh should refer to mmap'able file. 441 to a socket, and $in_fh should refer to an mmap'able file.
299 442
300 If the native sendfile call fails or is not implemented, it will be 443 If a native sendfile cannot be found or it fails with "ENOSYS",
301 emulated, so you can call "aio_sendfile" on any type of filehandle 444 "EINVAL", "ENOTSUP", "EOPNOTSUPP", "EAFNOSUPPORT", "EPROTOTYPE" or
302 regardless of the limitations of the operating system. 445 "ENOTSOCK", it will be emulated, so you can call "aio_sendfile" on
446 any type of filehandle regardless of the limitations of the
447 operating system.
303 448
304 Please note, however, that "aio_sendfile" can read more bytes from 449 As native sendfile syscalls (as practically any non-POSIX interface
305 $in_fh than are written, and there is no way to find out how many 450 hacked together in a hurry to improve benchmark numbers) tend to be
306 bytes have been read from "aio_sendfile" alone, as "aio_sendfile" 451 rather buggy on many systems, this implementation tries to work
307 only provides the number of bytes written to $out_fh. Only if the 452 around some known bugs in Linux and FreeBSD kernels (probably
308 result value equals $length one can assume that $length bytes have 453 others, too), but that might fail, so you really really should check
309 been read. 454 the return value of "aio_sendfile" - fewer bytes than expected might
455 have been transferred.
310 456
311 aio_readahead $fh,$offset,$length, $callback->($retval) 457 aio_readahead $fh,$offset,$length, $callback->($retval)
312 "aio_readahead" populates the page cache with data from a file so 458 "aio_readahead" populates the page cache with data from a file so
313 that subsequent reads from that file will not block on disk I/O. The 459 that subsequent reads from that file will not block on disk I/O. The
314 $offset argument specifies the starting point from which data is to 460 $offset argument specifies the starting point from which data is to
… …
317 to a page boundary and bytes are read up to the next page boundary 463 to a page boundary and bytes are read up to the next page boundary
318 greater than or equal to (off-set+length). "aio_readahead" does not 464 greater than or equal to (off-set+length). "aio_readahead" does not
319 read beyond the end of the file. The current file offset of the file 465 read beyond the end of the file. The current file offset of the file
320 is left unchanged. 466 is left unchanged.
321 467
322 If that syscall doesn't exist (likely if your OS isn't Linux) it 468 If that syscall doesn't exist (likely if your kernel isn't Linux) it
323 will be emulated by simply reading the data, which would have a 469 will be emulated by simply reading the data, which would have a
324 similar effect. 470 similar effect.
325 471
326 aio_stat $fh_or_path, $callback->($status) 472 aio_stat $fh_or_path, $callback->($status)
327 aio_lstat $fh, $callback->($status) 473 aio_lstat $fh, $callback->($status)
328 Works like perl's "stat" or "lstat" in void context. The callback 474 Works almost exactly like perl's "stat" or "lstat" in void context.
329 will be called after the stat and the results will be available 475 The callback will be called after the stat and the results will be
330 using "stat _" or "-s _" etc... 476 available using "stat _" or "-s _" and other tests (with the
477 exception of "-B" and "-T").
331 478
332 The pathname passed to "aio_stat" must be absolute. See API NOTES, 479 The pathname passed to "aio_stat" must be absolute. See API NOTES,
333 above, for an explanation. 480 above, for an explanation.
334 481
335 Currently, the stats are always 64-bit-stats, i.e. instead of 482 Currently, the stats are always 64-bit-stats, i.e. instead of
336 returning an error when stat'ing a large file, the results will be 483 returning an error when stat'ing a large file, the results will be
337 silently truncated unless perl itself is compiled with large file 484 silently truncated unless perl itself is compiled with large file
338 support. 485 support.
339 486
487 To help interpret the mode and dev/rdev stat values, IO::AIO offers
488 the following constants and functions (if not implemented, the
489 constants will be 0 and the functions will either "croak" or fall
490 back on traditional behaviour).
491
492 "S_IFMT", "S_IFIFO", "S_IFCHR", "S_IFBLK", "S_IFLNK", "S_IFREG",
493 "S_IFDIR", "S_IFWHT", "S_IFSOCK", "IO::AIO::major $dev_t",
494 "IO::AIO::minor $dev_t", "IO::AIO::makedev $major, $minor".
495
496 To access higher resolution stat timestamps, see "SUBSECOND STAT
497 TIME ACCESS".
498
340 Example: Print the length of /etc/passwd: 499 Example: Print the length of /etc/passwd:
341 500
342 aio_stat "/etc/passwd", sub { 501 aio_stat "/etc/passwd", sub {
343 $_[0] and die "stat failed: $!"; 502 $_[0] and die "stat failed: $!";
344 print "size is ", -s _, "\n"; 503 print "size is ", -s _, "\n";
345 }; 504 };
346 505
506 aio_statvfs $fh_or_path, $callback->($statvfs)
507 Works like the POSIX "statvfs" or "fstatvfs" syscalls, depending on
508 whether a file handle or path was passed.
509
510 On success, the callback is passed a hash reference with the
511 following members: "bsize", "frsize", "blocks", "bfree", "bavail",
512 "files", "ffree", "favail", "fsid", "flag" and "namemax". On
513 failure, "undef" is passed.
514
515 The following POSIX IO::AIO::ST_* constants are defined: "ST_RDONLY"
516 and "ST_NOSUID".
517
518 The following non-POSIX IO::AIO::ST_* flag masks are defined to
519 their correct value when available, or to 0 on systems that do not
520 support them: "ST_NODEV", "ST_NOEXEC", "ST_SYNCHRONOUS",
521 "ST_MANDLOCK", "ST_WRITE", "ST_APPEND", "ST_IMMUTABLE",
522 "ST_NOATIME", "ST_NODIRATIME" and "ST_RELATIME".
523
524 Example: stat "/wd" and dump out the data if successful.
525
526 aio_statvfs "/wd", sub {
527 my $f = $_[0]
528 or die "statvfs: $!";
529
530 use Data::Dumper;
531 say Dumper $f;
532 };
533
534 # result:
535 {
536 bsize => 1024,
537 bfree => 4333064312,
538 blocks => 10253828096,
539 files => 2050765568,
540 flag => 4096,
541 favail => 2042092649,
542 bavail => 4333064312,
543 ffree => 2042092649,
544 namemax => 255,
545 frsize => 1024,
546 fsid => 1810
547 }
548
549 aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
550 Works like perl's "utime" function (including the special case of
551 $atime and $mtime being undef). Fractional times are supported if
552 the underlying syscalls support them.
553
554 When called with a pathname, uses utimensat(2) or utimes(2) if
555 available, otherwise utime(2). If called on a file descriptor, uses
556 futimens(2) or futimes(2) if available, otherwise returns ENOSYS, so
557 this is not portable.
558
559 Examples:
560
561 # set atime and mtime to current time (basically touch(1)):
562 aio_utime "path", undef, undef;
563 # set atime to current time and mtime to beginning of the epoch:
564 aio_utime "path", time, undef; # undef==0
565
566 aio_chown $fh_or_path, $uid, $gid, $callback->($status)
567 Works like perl's "chown" function, except that "undef" for either
568 $uid or $gid is being interpreted as "do not change" (but -1 can
569 also be used).
570
571 Examples:
572
573 # same as "chown root path" in the shell:
574 aio_chown "path", 0, -1;
575 # same as above:
576 aio_chown "path", 0, undef;
577
578 aio_truncate $fh_or_path, $offset, $callback->($status)
579 Works like truncate(2) or ftruncate(2).
580
581 aio_allocate $fh, $mode, $offset, $len, $callback->($status)
582 Allocates or frees disk space according to the $mode argument. See
583 the linux "fallocate" documentation for details.
584
585 $mode is usually 0 or "IO::AIO::FALLOC_FL_KEEP_SIZE" to allocate
586 space, or "IO::AIO::FALLOC_FL_PUNCH_HOLE |
587 IO::AIO::FALLOC_FL_KEEP_SIZE", to deallocate a file range.
588
589 IO::AIO also supports "FALLOC_FL_COLLAPSE_RANGE", to remove a range
590 (without leaving a hole), "FALLOC_FL_ZERO_RANGE", to zero a range,
591 "FALLOC_FL_INSERT_RANGE" to insert a range and
592 "FALLOC_FL_UNSHARE_RANGE" to unshare shared blocks (see your
593 fallocate(2) manpage).
594
595 The file system block size used by "fallocate" is presumably the
596 "f_bsize" returned by "statvfs", but different filesystems and
597 filetypes can dictate other limitations.
598
599 If "fallocate" isn't available or cannot be emulated (currently no
600 emulation will be attempted), passes -1 and sets $! to "ENOSYS".
601
602 aio_chmod $fh_or_path, $mode, $callback->($status)
603 Works like perl's "chmod" function.
604
347 aio_unlink $pathname, $callback->($status) 605 aio_unlink $pathname, $callback->($status)
348 Asynchronously unlink (delete) a file and call the callback with the 606 Asynchronously unlink (delete) a file and call the callback with the
349 result code. 607 result code.
350 608
351 aio_mknod $path, $mode, $dev, $callback->($status) 609 aio_mknod $pathname, $mode, $dev, $callback->($status)
352 [EXPERIMENTAL] 610 [EXPERIMENTAL]
353 611
354 Asynchronously create a device node (or fifo). See mknod(2). 612 Asynchronously create a device node (or fifo). See mknod(2).
355 613
356 The only (POSIX-) portable way of calling this function is: 614 The only (POSIX-) portable way of calling this function is:
357 615
358 aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ... 616 aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
617
618 See "aio_stat" for info about some potentially helpful extra
619 constants and functions.
359 620
360 aio_link $srcpath, $dstpath, $callback->($status) 621 aio_link $srcpath, $dstpath, $callback->($status)
361 Asynchronously create a new link to the existing object at $srcpath 622 Asynchronously create a new link to the existing object at $srcpath
362 at the path $dstpath and call the callback with the result code. 623 at the path $dstpath and call the callback with the result code.
363 624
364 aio_symlink $srcpath, $dstpath, $callback->($status) 625 aio_symlink $srcpath, $dstpath, $callback->($status)
365 Asynchronously create a new symbolic link to the existing object at 626 Asynchronously create a new symbolic link to the existing object at
366 $srcpath at the path $dstpath and call the callback with the result 627 $srcpath at the path $dstpath and call the callback with the result
367 code. 628 code.
368 629
369 aio_readlink $path, $callback->($link) 630 aio_readlink $pathname, $callback->($link)
370 Asynchronously read the symlink specified by $path and pass it to 631 Asynchronously read the symlink specified by $path and pass it to
371 the callback. If an error occurs, nothing or undef gets passed to 632 the callback. If an error occurs, nothing or undef gets passed to
372 the callback. 633 the callback.
373 634
635 aio_realpath $pathname, $callback->($path)
636 Asynchronously make the path absolute and resolve any symlinks in
637 $path. The resulting path only consists of directories (same as
638 Cwd::realpath).
639
640 This request can be used to get the absolute path of the current
641 working directory by passing it a path of . (a single dot).
642
374 aio_rename $srcpath, $dstpath, $callback->($status) 643 aio_rename $srcpath, $dstpath, $callback->($status)
375 Asynchronously rename the object at $srcpath to $dstpath, just as 644 Asynchronously rename the object at $srcpath to $dstpath, just as
376 rename(2) and call the callback with the result code. 645 rename(2) and call the callback with the result code.
377 646
647 On systems that support the AIO::WD working directory abstraction
648 natively, the case "[$wd, "."]" as $srcpath is specialcased -
649 instead of failing, "rename" is called on the absolute path of $wd.
650
651 aio_rename2 $srcpath, $dstpath, $flags, $callback->($status)
652 Basically a version of "aio_rename" with an additional $flags
653 argument. Calling this with "$flags=0" is the same as calling
654 "aio_rename".
655
656 Non-zero flags are currently only supported on GNU/Linux systems
657 that support renameat2. Other systems fail with "ENOSYS" in this
658 case.
659
660 The following constants are available (missing ones are, as usual
661 0), see renameat2(2) for details:
662
663 "IO::AIO::RENAME_NOREPLACE", "IO::AIO::RENAME_EXCHANGE" and
664 "IO::AIO::RENAME_WHITEOUT".
665
666 aio_mkdir $pathname, $mode, $callback->($status)
667 Asynchronously mkdir (create) a directory and call the callback with
668 the result code. $mode will be modified by the umask at the time the
669 request is executed, so do not change your umask.
670
378 aio_rmdir $pathname, $callback->($status) 671 aio_rmdir $pathname, $callback->($status)
379 Asynchronously rmdir (delete) a directory and call the callback with 672 Asynchronously rmdir (delete) a directory and call the callback with
380 the result code. 673 the result code.
674
675 On systems that support the AIO::WD working directory abstraction
676 natively, the case "[$wd, "."]" is specialcased - instead of
677 failing, "rmdir" is called on the absolute path of $wd.
381 678
382 aio_readdir $pathname, $callback->($entries) 679 aio_readdir $pathname, $callback->($entries)
383 Unlike the POSIX call of the same name, "aio_readdir" reads an 680 Unlike the POSIX call of the same name, "aio_readdir" reads an
384 entire directory (i.e. opendir + readdir + closedir). The entries 681 entire directory (i.e. opendir + readdir + closedir). The entries
385 will not be sorted, and will NOT include the "." and ".." entries. 682 will not be sorted, and will NOT include the "." and ".." entries.
386 683
387 The callback a single argument which is either "undef" or an 684 The callback is passed a single argument which is either "undef" or
388 array-ref with the filenames. 685 an array-ref with the filenames.
686
687 aio_readdirx $pathname, $flags, $callback->($entries, $flags)
688 Quite similar to "aio_readdir", but the $flags argument allows one
689 to tune behaviour and output format. In case of an error, $entries
690 will be "undef".
691
692 The flags are a combination of the following constants, ORed
693 together (the flags will also be passed to the callback, possibly
694 modified):
695
696 IO::AIO::READDIR_DENTS
697 Normally the callback gets an arrayref consisting of names only
698 (as with "aio_readdir"). If this flag is set, then the callback
699 gets an arrayref with "[$name, $type, $inode]" arrayrefs, each
700 describing a single directory entry in more detail:
701
702 $name is the name of the entry.
703
704 $type is one of the "IO::AIO::DT_xxx" constants:
705
706 "IO::AIO::DT_UNKNOWN", "IO::AIO::DT_FIFO", "IO::AIO::DT_CHR",
707 "IO::AIO::DT_DIR", "IO::AIO::DT_BLK", "IO::AIO::DT_REG",
708 "IO::AIO::DT_LNK", "IO::AIO::DT_SOCK", "IO::AIO::DT_WHT".
709
710 "IO::AIO::DT_UNKNOWN" means just that: readdir does not know. If
711 you need to know, you have to run stat yourself. Also, for
712 speed/memory reasons, the $type scalars are read-only: you must
713 not modify them.
714
715 $inode is the inode number (which might not be exact on systems
716 with 64 bit inode numbers and 32 bit perls). This field has
717 unspecified content on systems that do not deliver the inode
718 information.
719
720 IO::AIO::READDIR_DIRS_FIRST
721 When this flag is set, then the names will be returned in an
722 order where likely directories come first, in optimal stat
723 order. This is useful when you need to quickly find directories,
724 or you want to find all directories while avoiding to stat()
725 each entry.
726
727 If the system returns type information in readdir, then this is
728 used to find directories directly. Otherwise, likely directories
729 are names beginning with ".", or otherwise names with no dots,
730 of which names with short names are tried first.
731
732 IO::AIO::READDIR_STAT_ORDER
733 When this flag is set, then the names will be returned in an
734 order suitable for stat()'ing each one. That is, when you plan
735 to stat() most or all files in the given directory, then the
736 returned order will likely be faster.
737
738 If both this flag and "IO::AIO::READDIR_DIRS_FIRST" are
739 specified, then the likely dirs come first, resulting in a less
740 optimal stat order for stat'ing all entries, but likely a more
741 optimal order for finding subdirectories.
742
743 IO::AIO::READDIR_FOUND_UNKNOWN
744 This flag should not be set when calling "aio_readdirx".
745 Instead, it is being set by "aio_readdirx", when any of the
746 $type's found were "IO::AIO::DT_UNKNOWN". The absence of this
747 flag therefore indicates that all $type's are known, which can
748 be used to speed up some algorithms.
749
750 aio_slurp $pathname, $offset, $length, $data, $callback->($status)
751 Opens, reads and closes the given file. The data is put into $data,
752 which is resized as required.
753
754 If $offset is negative, then it is counted from the end of the file.
755
756 If $length is zero, then the remaining length of the file is used.
757 Also, in this case, the same limitations to modifying $data apply as
758 when IO::AIO::mmap is used, i.e. it must only be modified in-place
759 with "substr". If the size of the file is known, specifying a
760 non-zero $length results in a performance advantage.
761
762 This request is similar to the older "aio_load" request, but since
763 it is a single request, it might be more efficient to use.
764
765 Example: load /etc/passwd into $passwd.
766
767 my $passwd;
768 aio_slurp "/etc/passwd", 0, 0, $passwd, sub {
769 $_[0] >= 0
770 or die "/etc/passwd: $!\n";
771
772 printf "/etc/passwd is %d bytes long, and contains:\n", length $passwd;
773 print $passwd;
774 };
775 IO::AIO::flush;
776
777 aio_load $pathname, $data, $callback->($status)
778 This is a composite request that tries to fully load the given file
779 into memory. Status is the same as with aio_read.
780
781 Using "aio_slurp" might be more efficient, as it is a single
782 request.
389 783
390 aio_copy $srcpath, $dstpath, $callback->($status) 784 aio_copy $srcpath, $dstpath, $callback->($status)
391 Try to copy the *file* (directories not supported as either source 785 Try to copy the *file* (directories not supported as either source
392 or destination) from $srcpath to $dstpath and call the callback with 786 or destination) from $srcpath to $dstpath and call the callback with
393 the 0 (error) or -1 ok. 787 a status of 0 (ok) or -1 (error, see $!).
394 788
789 Existing destination files will be truncated.
790
395 This is a composite request that it creates the destination file 791 This is a composite request that creates the destination file with
396 with mode 0200 and copies the contents of the source file into it 792 mode 0200 and copies the contents of the source file into it using
397 using "aio_sendfile", followed by restoring atime, mtime, access 793 "aio_sendfile", followed by restoring atime, mtime, access mode and
398 mode and uid/gid, in that order. 794 uid/gid, in that order.
399 795
400 If an error occurs, the partial destination file will be unlinked, 796 If an error occurs, the partial destination file will be unlinked,
401 if possible, except when setting atime, mtime, access mode and 797 if possible, except when setting atime, mtime, access mode and
402 uid/gid, where errors are being ignored. 798 uid/gid, where errors are being ignored.
403 799
404 aio_move $srcpath, $dstpath, $callback->($status) 800 aio_move $srcpath, $dstpath, $callback->($status)
405 Try to move the *file* (directories not supported as either source 801 Try to move the *file* (directories not supported as either source
406 or destination) from $srcpath to $dstpath and call the callback with 802 or destination) from $srcpath to $dstpath and call the callback with
407 the 0 (error) or -1 ok. 803 a status of 0 (ok) or -1 (error, see $!).
408 804
409 This is a composite request that tries to rename(2) the file first. 805 This is a composite request that tries to rename(2) the file first;
410 If rename files with "EXDEV", it copies the file with "aio_copy" 806 if rename fails with "EXDEV", it copies the file with "aio_copy"
411 and, if that is successful, unlinking the $srcpath. 807 and, if that is successful, unlinks the $srcpath.
412 808
413 aio_scandir $path, $maxreq, $callback->($dirs, $nondirs) 809 aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
414 Scans a directory (similar to "aio_readdir") but additionally tries 810 Scans a directory (similar to "aio_readdir") but additionally tries
415 to efficiently separate the entries of directory $path into two sets 811 to efficiently separate the entries of directory $path into two sets
416 of names, directories you can recurse into (directories), and ones 812 of names, directories you can recurse into (directories), and ones
417 you cannot recurse into (everything else, including symlinks to 813 you cannot recurse into (everything else, including symlinks to
418 directories). 814 directories).
419 815
420 "aio_scandir" is a composite request that creates of many sub 816 "aio_scandir" is a composite request that generates many sub
421 requests_ $maxreq specifies the maximum number of outstanding aio 817 requests. $maxreq specifies the maximum number of outstanding aio
422 requests that this function generates. If it is "<= 0", then a 818 requests that this function generates. If it is "<= 0", then a
423 suitable default will be chosen (currently 4). 819 suitable default will be chosen (currently 4).
424 820
425 On error, the callback is called without arguments, otherwise it 821 On error, the callback is called without arguments, otherwise it
426 receives two array-refs with path-relative entry names. 822 receives two array-refs with path-relative entry names.
… …
436 Implementation notes. 832 Implementation notes.
437 833
438 The "aio_readdir" cannot be avoided, but "stat()"'ing every entry 834 The "aio_readdir" cannot be avoided, but "stat()"'ing every entry
439 can. 835 can.
440 836
837 If readdir returns file type information, then this is used directly
838 to find directories.
839
441 After reading the directory, the modification time, size etc. of the 840 Otherwise, after reading the directory, the modification time, size
442 directory before and after the readdir is checked, and if they match 841 etc. of the directory before and after the readdir is checked, and
443 (and isn't the current time), the link count will be used to decide 842 if they match (and isn't the current time), the link count will be
444 how many entries are directories (if >= 2). Otherwise, no knowledge 843 used to decide how many entries are directories (if >= 2).
445 of the number of subdirectories will be assumed. 844 Otherwise, no knowledge of the number of subdirectories will be
845 assumed.
446 846
447 Then entries will be sorted into likely directories (everything 847 Then entries will be sorted into likely directories a non-initial
448 without a non-initial dot currently) and likely non-directories 848 dot currently) and likely non-directories (see "aio_readdirx"). Then
449 (everything else). Then every entry plus an appended "/." will be 849 every entry plus an appended "/." will be "stat"'ed, likely
450 "stat"'ed, likely directories first. If that succeeds, it assumes 850 directories first, in order of their inode numbers. If that
451 that the entry is a directory or a symlink to directory (which will 851 succeeds, it assumes that the entry is a directory or a symlink to
452 be checked seperately). This is often faster than stat'ing the entry 852 directory (which will be checked separately). This is often faster
453 itself because filesystems might detect the type of the entry 853 than stat'ing the entry itself because filesystems might detect the
454 without reading the inode data (e.g. ext2fs filetype feature). 854 type of the entry without reading the inode data (e.g. ext2fs
855 filetype feature), even on systems that cannot return the filetype
856 information on readdir.
455 857
456 If the known number of directories (link count - 2) has been 858 If the known number of directories (link count - 2) has been
457 reached, the rest of the entries is assumed to be non-directories. 859 reached, the rest of the entries is assumed to be non-directories.
458 860
459 This only works with certainty on POSIX (= UNIX) filesystems, which 861 This only works with certainty on POSIX (= UNIX) filesystems, which
… …
461 863
462 It will also likely work on non-POSIX filesystems with reduced 864 It will also likely work on non-POSIX filesystems with reduced
463 efficiency as those tend to return 0 or 1 as link counts, which 865 efficiency as those tend to return 0 or 1 as link counts, which
464 disables the directory counting heuristic. 866 disables the directory counting heuristic.
465 867
868 aio_rmtree $pathname, $callback->($status)
869 Delete a directory tree starting (and including) $path, return the
870 status of the final "rmdir" only. This is a composite request that
871 uses "aio_scandir" to recurse into and rmdir directories, and unlink
872 everything else.
873
874 aio_fcntl $fh, $cmd, $arg, $callback->($status)
875 aio_ioctl $fh, $request, $buf, $callback->($status)
876 These work just like the "fcntl" and "ioctl" built-in functions,
877 except they execute asynchronously and pass the return value to the
878 callback.
879
880 Both calls can be used for a lot of things, some of which make more
881 sense to run asynchronously in their own thread, while some others
882 make less sense. For example, calls that block waiting for external
883 events, such as locking, will also lock down an I/O thread while it
884 is waiting, which can deadlock the whole I/O system. At the same
885 time, there might be no alternative to using a thread to wait.
886
887 So in general, you should only use these calls for things that do
888 (filesystem) I/O, not for things that wait for other events
889 (network, other processes), although if you are careful and know
890 what you are doing, you still can.
891
892 The following constants are available (missing ones are, as usual
893 0):
894
895 "F_DUPFD_CLOEXEC",
896
897 "F_OFD_GETLK", "F_OFD_SETLK", "F_OFD_GETLKW",
898
899 "FIFREEZE", "FITHAW", "FITRIM", "FICLONE", "FICLONERANGE",
900 "FIDEDUPERANGE".
901
902 "FS_IOC_GETFLAGS", "FS_IOC_SETFLAGS", "FS_IOC_GETVERSION",
903 "FS_IOC_SETVERSION", "FS_IOC_FIEMAP".
904
905 "FS_IOC_FSGETXATTR", "FS_IOC_FSSETXATTR",
906 "FS_IOC_SET_ENCRYPTION_POLICY", "FS_IOC_GET_ENCRYPTION_PWSALT",
907 "FS_IOC_GET_ENCRYPTION_POLICY", "FS_KEY_DESCRIPTOR_SIZE".
908
909 "FS_SECRM_FL", "FS_UNRM_FL", "FS_COMPR_FL", "FS_SYNC_FL",
910 "FS_IMMUTABLE_FL", "FS_APPEND_FL", "FS_NODUMP_FL", "FS_NOATIME_FL",
911 "FS_DIRTY_FL", "FS_COMPRBLK_FL", "FS_NOCOMP_FL", "FS_ENCRYPT_FL",
912 "FS_BTREE_FL", "FS_INDEX_FL", "FS_JOURNAL_DATA_FL", "FS_NOTAIL_FL",
913 "FS_DIRSYNC_FL", "FS_TOPDIR_FL", "FS_FL_USER_MODIFIABLE".
914
915 "FS_XFLAG_REALTIME", "FS_XFLAG_PREALLOC", "FS_XFLAG_IMMUTABLE",
916 "FS_XFLAG_APPEND", "FS_XFLAG_SYNC", "FS_XFLAG_NOATIME",
917 "FS_XFLAG_NODUMP", "FS_XFLAG_RTINHERIT", "FS_XFLAG_PROJINHERIT",
918 "FS_XFLAG_NOSYMLINKS", "FS_XFLAG_EXTSIZE", "FS_XFLAG_EXTSZINHERIT",
919 "FS_XFLAG_NODEFRAG", "FS_XFLAG_FILESTREAM", "FS_XFLAG_DAX",
920 "FS_XFLAG_HASATTR",
921
922 aio_sync $callback->($status)
923 Asynchronously call sync and call the callback when finished.
924
466 aio_fsync $fh, $callback->($status) 925 aio_fsync $fh, $callback->($status)
467 Asynchronously call fsync on the given filehandle and call the 926 Asynchronously call fsync on the given filehandle and call the
468 callback with the fsync result code. 927 callback with the fsync result code.
469 928
470 aio_fdatasync $fh, $callback->($status) 929 aio_fdatasync $fh, $callback->($status)
471 Asynchronously call fdatasync on the given filehandle and call the 930 Asynchronously call fdatasync on the given filehandle and call the
472 callback with the fdatasync result code. 931 callback with the fdatasync result code.
473 932
474 If this call isn't available because your OS lacks it or it couldn't 933 If this call isn't available because your OS lacks it or it couldn't
475 be detected, it will be emulated by calling "fsync" instead. 934 be detected, it will be emulated by calling "fsync" instead.
935
936 aio_syncfs $fh, $callback->($status)
937 Asynchronously call the syncfs syscall to sync the filesystem
938 associated to the given filehandle and call the callback with the
939 syncfs result code. If syncfs is not available, calls sync(), but
940 returns -1 and sets errno to "ENOSYS" nevertheless.
941
942 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
943 Sync the data portion of the file specified by $offset and $length
944 to disk (but NOT the metadata), by calling the Linux-specific
945 sync_file_range call. If sync_file_range is not available or it
946 returns ENOSYS, then fdatasync or fsync is being substituted.
947
948 $flags can be a combination of
949 "IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE",
950 "IO::AIO::SYNC_FILE_RANGE_WRITE" and
951 "IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER": refer to the sync_file_range
952 manpage for details.
953
954 aio_pathsync $pathname, $callback->($status)
955 This request tries to open, fsync and close the given path. This is
956 a composite request intended to sync directories after directory
957 operations (E.g. rename). This might not work on all operating
958 systems or have any specific effect, but usually it makes sure that
959 directory changes get written to disc. It works for anything that
960 can be opened for read-only, not just directories.
961
962 Future versions of this function might fall back to other methods
963 when "fsync" on the directory fails (such as calling "sync").
964
965 Passes 0 when everything went ok, and -1 on error.
966
967 aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC,
968 $callback->($status)
969 This is a rather advanced IO::AIO call, which only works on
970 mmap(2)ed scalars (see the "IO::AIO::mmap" function, although it
971 also works on data scalars managed by the Sys::Mmap or Mmap modules,
972 note that the scalar must only be modified in-place while an aio
973 operation is pending on it).
974
975 It calls the "msync" function of your OS, if available, with the
976 memory area starting at $offset in the string and ending $length
977 bytes later. If $length is negative, counts from the end, and if
978 $length is "undef", then it goes till the end of the string. The
979 flags can be either "IO::AIO::MS_ASYNC" or "IO::AIO::MS_SYNC", plus
980 an optional "IO::AIO::MS_INVALIDATE".
981
982 aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0,
983 $callback->($status)
984 This is a rather advanced IO::AIO call, which works best on
985 mmap(2)ed scalars.
986
987 It touches (reads or writes) all memory pages in the specified range
988 inside the scalar. All caveats and parameters are the same as for
989 "aio_msync", above, except for flags, which must be either 0 (which
990 reads all pages and ensures they are instantiated) or
991 "IO::AIO::MT_MODIFY", which modifies the memory pages (by reading
992 and writing an octet from it, which dirties the page).
993
994 aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
995 This is a rather advanced IO::AIO call, which works best on
996 mmap(2)ed scalars.
997
998 It reads in all the pages of the underlying storage into memory (if
999 any) and locks them, so they are not getting swapped/paged out or
1000 removed.
1001
1002 If $length is undefined, then the scalar will be locked till the
1003 end.
1004
1005 On systems that do not implement "mlock", this function returns -1
1006 and sets errno to "ENOSYS".
1007
1008 Note that the corresponding "munlock" is synchronous and is
1009 documented under "MISCELLANEOUS FUNCTIONS".
1010
1011 Example: open a file, mmap and mlock it - both will be undone when
1012 $data gets destroyed.
1013
1014 open my $fh, "<", $path or die "$path: $!";
1015 my $data;
1016 IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
1017 aio_mlock $data; # mlock in background
1018
1019 aio_mlockall $flags, $callback->($status)
1020 Calls the "mlockall" function with the given $flags (a combination
1021 of "IO::AIO::MCL_CURRENT", "IO::AIO::MCL_FUTURE" and
1022 "IO::AIO::MCL_ONFAULT").
1023
1024 On systems that do not implement "mlockall", this function returns
1025 -1 and sets errno to "ENOSYS". Similarly, flag combinations not
1026 supported by the system result in a return value of -1 with errno
1027 being set to "EINVAL".
1028
1029 Note that the corresponding "munlockall" is synchronous and is
1030 documented under "MISCELLANEOUS FUNCTIONS".
1031
1032 Example: asynchronously lock all current and future pages into
1033 memory.
1034
1035 aio_mlockall IO::AIO::MCL_FUTURE;
1036
1037 aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
1038 Queries the extents of the given file (by calling the Linux "FIEMAP"
1039 ioctl, see <http://cvs.schmorp.de/IO-AIO/doc/fiemap.txt> for
1040 details). If the ioctl is not available on your OS, then this
1041 request will fail with "ENOSYS".
1042
1043 $start is the starting offset to query extents for, $length is the
1044 size of the range to query - if it is "undef", then the whole file
1045 will be queried.
1046
1047 $flags is a combination of flags ("IO::AIO::FIEMAP_FLAG_SYNC" or
1048 "IO::AIO::FIEMAP_FLAG_XATTR" - "IO::AIO::FIEMAP_FLAGS_COMPAT" is
1049 also exported), and is normally 0 or "IO::AIO::FIEMAP_FLAG_SYNC" to
1050 query the data portion.
1051
1052 $count is the maximum number of extent records to return. If it is
1053 "undef", then IO::AIO queries all extents of the range. As a very
1054 special case, if it is 0, then the callback receives the number of
1055 extents instead of the extents themselves (which is unreliable, see
1056 below).
1057
1058 If an error occurs, the callback receives no arguments. The special
1059 "errno" value "IO::AIO::EBADR" is available to test for flag errors.
1060
1061 Otherwise, the callback receives an array reference with extent
1062 structures. Each extent structure is an array reference itself, with
1063 the following members:
1064
1065 [$logical, $physical, $length, $flags]
1066
1067 Flags is any combination of the following flag values (typically
1068 either 0 or "IO::AIO::FIEMAP_EXTENT_LAST" (1)):
1069
1070 "IO::AIO::FIEMAP_EXTENT_LAST", "IO::AIO::FIEMAP_EXTENT_UNKNOWN",
1071 "IO::AIO::FIEMAP_EXTENT_DELALLOC", "IO::AIO::FIEMAP_EXTENT_ENCODED",
1072 "IO::AIO::FIEMAP_EXTENT_DATA_ENCRYPTED",
1073 "IO::AIO::FIEMAP_EXTENT_NOT_ALIGNED",
1074 "IO::AIO::FIEMAP_EXTENT_DATA_INLINE",
1075 "IO::AIO::FIEMAP_EXTENT_DATA_TAIL",
1076 "IO::AIO::FIEMAP_EXTENT_UNWRITTEN", "IO::AIO::FIEMAP_EXTENT_MERGED"
1077 or "IO::AIO::FIEMAP_EXTENT_SHARED".
1078
1079 At the time of this writing (Linux 3.2), this request is unreliable
1080 unless $count is "undef", as the kernel has all sorts of bugs
1081 preventing it to return all extents of a range for files with a
1082 large number of extents. The code (only) works around all these
1083 issues if $count is "undef".
476 1084
477 aio_group $callback->(...) 1085 aio_group $callback->(...)
478 This is a very special aio request: Instead of doing something, it 1086 This is a very special aio request: Instead of doing something, it
479 is a container for other aio requests, which is useful if you want 1087 is a container for other aio requests, which is useful if you want
480 to bundle many requests into a single, composite, request with a 1088 to bundle many requests into a single, composite, request with a
… …
515 requests like sleep and file handle readable/writable, the overhead 1123 requests like sleep and file handle readable/writable, the overhead
516 this creates is immense (it blocks a thread for a long time) so do 1124 this creates is immense (it blocks a thread for a long time) so do
517 not use this function except to put your application under 1125 not use this function except to put your application under
518 artificial I/O pressure. 1126 artificial I/O pressure.
519 1127
1128 IO::AIO::WD - multiple working directories
1129 Your process only has one current working directory, which is used by
1130 all threads. This makes it hard to use relative paths (some other
1131 component could call "chdir" at any time, and it is hard to control when
1132 the path will be used by IO::AIO).
1133
1134 One solution for this is to always use absolute paths. This usually
1135 works, but can be quite slow (the kernel has to walk the whole path on
1136 every access), and can also be a hassle to implement.
1137
1138 Newer POSIX systems have a number of functions (openat, fdopendir,
1139 futimensat and so on) that make it possible to specify working
1140 directories per operation.
1141
1142 For portability, and because the clowns who "designed", or shall I
1143 write, perpetrated this new interface were obviously half-drunk, this
1144 abstraction cannot be perfect, though.
1145
1146 IO::AIO allows you to convert directory paths into a so-called
1147 IO::AIO::WD object. This object stores the canonicalised, absolute
1148 version of the path, and on systems that allow it, also a directory file
1149 descriptor.
1150
1151 Everywhere where a pathname is accepted by IO::AIO (e.g. in "aio_stat"
1152 or "aio_unlink"), one can specify an array reference with an IO::AIO::WD
1153 object and a pathname instead (or the IO::AIO::WD object alone, which
1154 gets interpreted as "[$wd, "."]"). If the pathname is absolute, the
1155 IO::AIO::WD object is ignored, otherwise the pathname is resolved
1156 relative to that IO::AIO::WD object.
1157
1158 For example, to get a wd object for /etc and then stat passwd inside,
1159 you would write:
1160
1161 aio_wd "/etc", sub {
1162 my $etcdir = shift;
1163
1164 # although $etcdir can be undef on error, there is generally no reason
1165 # to check for errors here, as aio_stat will fail with ENOENT
1166 # when $etcdir is undef.
1167
1168 aio_stat [$etcdir, "passwd"], sub {
1169 # yay
1170 };
1171 };
1172
1173 The fact that "aio_wd" is a request and not a normal function shows that
1174 creating an IO::AIO::WD object is itself a potentially blocking
1175 operation, which is why it is done asynchronously.
1176
1177 To stat the directory obtained with "aio_wd" above, one could write
1178 either of the following three request calls:
1179
1180 aio_lstat "/etc" , sub { ... # pathname as normal string
1181 aio_lstat [$wd, "."], sub { ... # "." relative to $wd (i.e. $wd itself)
1182 aio_lstat $wd , sub { ... # shorthand for the previous
1183
1184 As with normal pathnames, IO::AIO keeps a copy of the working directory
1185 object and the pathname string, so you could write the following without
1186 causing any issues due to $path getting reused:
1187
1188 my $path = [$wd, undef];
1189
1190 for my $name (qw(abc def ghi)) {
1191 $path->[1] = $name;
1192 aio_stat $path, sub {
1193 # ...
1194 };
1195 }
1196
1197 There are some caveats: when directories get renamed (or deleted), the
1198 pathname string doesn't change, so will point to the new directory (or
1199 nowhere at all), while the directory fd, if available on the system,
1200 will still point to the original directory. Most functions accepting a
1201 pathname will use the directory fd on newer systems, and the string on
1202 older systems. Some functions (such as "aio_realpath") will always rely
1203 on the string form of the pathname.
1204
1205 So this functionality is mainly useful to get some protection against
1206 "chdir", to easily get an absolute path out of a relative path for
1207 future reference, and to speed up doing many operations in the same
1208 directory (e.g. when stat'ing all files in a directory).
1209
1210 The following functions implement this working directory abstraction:
1211
1212 aio_wd $pathname, $callback->($wd)
1213 Asynchonously canonicalise the given pathname and convert it to an
1214 IO::AIO::WD object representing it. If possible and supported on the
1215 system, also open a directory fd to speed up pathname resolution
1216 relative to this working directory.
1217
1218 If something goes wrong, then "undef" is passwd to the callback
1219 instead of a working directory object and $! is set appropriately.
1220 Since passing "undef" as working directory component of a pathname
1221 fails the request with "ENOENT", there is often no need for error
1222 checking in the "aio_wd" callback, as future requests using the
1223 value will fail in the expected way.
1224
1225 IO::AIO::CWD
1226 This is a compiletime constant (object) that represents the process
1227 current working directory.
1228
1229 Specifying this object as working directory object for a pathname is
1230 as if the pathname would be specified directly, without a directory
1231 object. For example, these calls are functionally identical:
1232
1233 aio_stat "somefile", sub { ... };
1234 aio_stat [IO::AIO::CWD, "somefile"], sub { ... };
1235
1236 To recover the path associated with an IO::AIO::WD object, you can use
1237 "aio_realpath":
1238
1239 aio_realpath $wd, sub {
1240 warn "path is $_[0]\n";
1241 };
1242
1243 Currently, "aio_statvfs" always, and "aio_rename" and "aio_rmdir"
1244 sometimes, fall back to using an absolue path.
1245
520 IO::AIO::REQ CLASS 1246 IO::AIO::REQ CLASS
521 All non-aggregate "aio_*" functions return an object of this class when 1247 All non-aggregate "aio_*" functions return an object of this class when
522 called in non-void context. 1248 called in non-void context.
523 1249
524 cancel $req 1250 cancel $req
525 Cancels the request, if possible. Has the effect of skipping 1251 Cancels the request, if possible. Has the effect of skipping
526 execution when entering the execute state and skipping calling the 1252 execution when entering the execute state and skipping calling the
527 callback when entering the the result state, but will leave the 1253 callback when entering the the result state, but will leave the
528 request otherwise untouched. That means that requests that currently 1254 request otherwise untouched (with the exception of readdir). That
529 execute will not be stopped and resources held by the request will 1255 means that requests that currently execute will not be stopped and
530 not be freed prematurely. 1256 resources held by the request will not be freed prematurely.
531 1257
532 cb $req $callback->(...) 1258 cb $req $callback->(...)
533 Replace (or simply set) the callback registered to the request. 1259 Replace (or simply set) the callback registered to the request.
534 1260
535 IO::AIO::GRP CLASS 1261 IO::AIO::GRP CLASS
… …
562 }; 1288 };
563 1289
564 This makes it very easy to create composite requests (see the source of 1290 This makes it very easy to create composite requests (see the source of
565 "aio_move" for an application) that work and feel like simple requests. 1291 "aio_move" for an application) that work and feel like simple requests.
566 1292
567 * The IO::AIO::GRP objects will be cleaned up during calls to 1293 * The IO::AIO::GRP objects will be cleaned up during calls to
568 "IO::AIO::poll_cb", just like any other request. 1294 "IO::AIO::poll_cb", just like any other request.
1295
569 * They can be canceled like any other request. Canceling will cancel not 1296 * They can be canceled like any other request. Canceling will cancel
570 only the request itself, but also all requests it contains. 1297 not only the request itself, but also all requests it contains.
1298
571 * They can also can also be added to other IO::AIO::GRP objects. 1299 * They can also can also be added to other IO::AIO::GRP objects.
1300
572 * You must not add requests to a group from within the group callback 1301 * You must not add requests to a group from within the group callback
573 (or any later time). 1302 (or any later time).
574 1303
575 Their lifetime, simplified, looks like this: when they are empty, they 1304 Their lifetime, simplified, looks like this: when they are empty, they
576 will finish very quickly. If they contain only requests that are in the 1305 will finish very quickly. If they contain only requests that are in the
577 "done" state, they will also finish. Otherwise they will continue to 1306 "done" state, they will also finish. Otherwise they will continue to
578 exist. 1307 exist.
579 1308
580 That means after creating a group you have some time to add requests. 1309 That means after creating a group you have some time to add requests
581 And in the callbacks of those requests, you can add further requests to 1310 (precisely before the callback has been invoked, which is only done
582 the group. And only when all those requests have finished will the the 1311 within the "poll_cb"). And in the callbacks of those requests, you can
583 group itself finish. 1312 add further requests to the group. And only when all those requests have
1313 finished will the the group itself finish.
584 1314
585 add $grp ... 1315 add $grp ...
586 $grp->add (...) 1316 $grp->add (...)
587 Add one or more requests to the group. Any type of IO::AIO::REQ can 1317 Add one or more requests to the group. Any type of IO::AIO::REQ can
588 be added, including other groups, as long as you do not create 1318 be added, including other groups, as long as you do not create
… …
593 $grp->cancel_subs 1323 $grp->cancel_subs
594 Cancel all subrequests and clears any feeder, but not the group 1324 Cancel all subrequests and clears any feeder, but not the group
595 request itself. Useful when you queued a lot of events but got a 1325 request itself. Useful when you queued a lot of events but got a
596 result early. 1326 result early.
597 1327
1328 The group request will finish normally (you cannot add requests to
1329 the group).
1330
598 $grp->result (...) 1331 $grp->result (...)
599 Set the result value(s) that will be passed to the group callback 1332 Set the result value(s) that will be passed to the group callback
600 when all subrequests have finished and set thre groups errno to the 1333 when all subrequests have finished and set the groups errno to the
601 current value of errno (just like calling "errno" without an error 1334 current value of errno (just like calling "errno" without an error
602 number). By default, no argument will be passed and errno is zero. 1335 number). By default, no argument will be passed and errno is zero.
603 1336
604 $grp->errno ([$errno]) 1337 $grp->errno ([$errno])
605 Sets the group errno value to $errno, or the current value of errno 1338 Sets the group errno value to $errno, or the current value of errno
… …
616 Sets a feeder/generator on this group: every group can have an 1349 Sets a feeder/generator on this group: every group can have an
617 attached generator that generates requests if idle. The idea behind 1350 attached generator that generates requests if idle. The idea behind
618 this is that, although you could just queue as many requests as you 1351 this is that, although you could just queue as many requests as you
619 want in a group, this might starve other requests for a potentially 1352 want in a group, this might starve other requests for a potentially
620 long time. For example, "aio_scandir" might generate hundreds of 1353 long time. For example, "aio_scandir" might generate hundreds of
621 thousands "aio_stat" requests, delaying any later requests for a 1354 thousands of "aio_stat" requests, delaying any later requests for a
622 long time. 1355 long time.
623 1356
624 To avoid this, and allow incremental generation of requests, you can 1357 To avoid this, and allow incremental generation of requests, you can
625 instead a group and set a feeder on it that generates those 1358 instead a group and set a feeder on it that generates those
626 requests. The feed callback will be called whenever there are few 1359 requests. The feed callback will be called whenever there are few
… …
631 does not impose any limits). 1364 does not impose any limits).
632 1365
633 If the feed does not queue more requests when called, it will be 1366 If the feed does not queue more requests when called, it will be
634 automatically removed from the group. 1367 automatically removed from the group.
635 1368
636 If the feed limit is 0, it will be set to 2 automatically. 1369 If the feed limit is 0 when this method is called, it will be set to
1370 2 automatically.
637 1371
638 Example: 1372 Example:
639 1373
640 # stat all files in @files, but only ever use four aio requests concurrently: 1374 # stat all files in @files, but only ever use four aio requests concurrently:
641 1375
… …
652 Sets the feeder limit for the group: The feeder will be called 1386 Sets the feeder limit for the group: The feeder will be called
653 whenever the group contains less than this many requests. 1387 whenever the group contains less than this many requests.
654 1388
655 Setting the limit to 0 will pause the feeding process. 1389 Setting the limit to 0 will pause the feeding process.
656 1390
1391 The default value for the limit is 0, but note that setting a feeder
1392 automatically bumps it up to 2.
1393
657 SUPPORT FUNCTIONS 1394 SUPPORT FUNCTIONS
658 EVENT PROCESSING AND EVENT LOOP INTEGRATION 1395 EVENT PROCESSING AND EVENT LOOP INTEGRATION
659 $fileno = IO::AIO::poll_fileno 1396 $fileno = IO::AIO::poll_fileno
660 Return the *request result pipe file descriptor*. This filehandle 1397 Return the *request result pipe file descriptor*. This filehandle
661 must be polled for reading by some mechanism outside this module 1398 must be polled for reading by some mechanism outside this module
662 (e.g. Event or select, see below or the SYNOPSIS). If the pipe 1399 (e.g. EV, Glib, select and so on, see below or the SYNOPSIS). If the
663 becomes readable you have to call "poll_cb" to check the results. 1400 pipe becomes readable you have to call "poll_cb" to check the
1401 results.
664 1402
665 See "poll_cb" for an example. 1403 See "poll_cb" for an example.
666 1404
667 IO::AIO::poll_cb 1405 IO::AIO::poll_cb
668 Process some outstanding events on the result pipe. You have to call 1406 Process some requests that have reached the result phase (i.e. they
669 this regularly. Returns the number of events processed. Returns 1407 have been executed but the results are not yet reported). You have
1408 to call this "regularly" to finish outstanding requests.
1409
1410 Returns 0 if all events could be processed (or there were no events
1411 to process), or -1 if it returned earlier for whatever reason.
670 immediately when no events are outstanding. The amount of events 1412 Returns immediately when no events are outstanding. The amount of
671 processed depends on the settings of "IO::AIO::max_poll_req" and 1413 events processed depends on the settings of "IO::AIO::max_poll_req",
672 "IO::AIO::max_poll_time". 1414 "IO::AIO::max_poll_time" and "IO::AIO::max_outstanding".
673 1415
674 If not all requests were processed for whatever reason, the 1416 If not all requests were processed for whatever reason, the poll
675 filehandle will still be ready when "poll_cb" returns. 1417 file descriptor will still be ready when "poll_cb" returns, so
1418 normally you don't have to do anything special to have it called
1419 later.
1420
1421 Apart from calling "IO::AIO::poll_cb" when the event filehandle
1422 becomes ready, it can be beneficial to call this function from loops
1423 which submit a lot of requests, to make sure the results get
1424 processed when they become available and not just when the loop is
1425 finished and the event loop takes over again. This function returns
1426 very fast when there are no outstanding requests.
676 1427
677 Example: Install an Event watcher that automatically calls 1428 Example: Install an Event watcher that automatically calls
678 IO::AIO::poll_cb with high priority: 1429 IO::AIO::poll_cb with high priority (more examples can be found in
1430 the SYNOPSIS section, at the top of this document):
679 1431
680 Event->io (fd => IO::AIO::poll_fileno, 1432 Event->io (fd => IO::AIO::poll_fileno,
681 poll => 'r', async => 1, 1433 poll => 'r', async => 1,
682 cb => \&IO::AIO::poll_cb); 1434 cb => \&IO::AIO::poll_cb);
1435
1436 IO::AIO::poll_wait
1437 Wait until either at least one request is in the result phase or no
1438 requests are outstanding anymore.
1439
1440 This is useful if you want to synchronously wait for some requests
1441 to become ready, without actually handling them.
1442
1443 See "nreqs" for an example.
1444
1445 IO::AIO::poll
1446 Waits until some requests have been handled.
1447
1448 Returns the number of requests processed, but is otherwise strictly
1449 equivalent to:
1450
1451 IO::AIO::poll_wait, IO::AIO::poll_cb
1452
1453 IO::AIO::flush
1454 Wait till all outstanding AIO requests have been handled.
1455
1456 Strictly equivalent to:
1457
1458 IO::AIO::poll_wait, IO::AIO::poll_cb
1459 while IO::AIO::nreqs;
1460
1461 This function can be useful at program aborts, to make sure
1462 outstanding I/O has been done ("IO::AIO" uses an "END" block which
1463 already calls this function on normal exits), or when you are merely
1464 using "IO::AIO" for its more advanced functions, rather than for
1465 async I/O, e.g.:
1466
1467 my ($dirs, $nondirs);
1468 IO::AIO::aio_scandir "/tmp", 0, sub { ($dirs, $nondirs) = @_ };
1469 IO::AIO::flush;
1470 # $dirs, $nondirs are now set
683 1471
684 IO::AIO::max_poll_reqs $nreqs 1472 IO::AIO::max_poll_reqs $nreqs
685 IO::AIO::max_poll_time $seconds 1473 IO::AIO::max_poll_time $seconds
686 These set the maximum number of requests (default 0, meaning 1474 These set the maximum number of requests (default 0, meaning
687 infinity) that are being processed by "IO::AIO::poll_cb" in one 1475 infinity) that are being processed by "IO::AIO::poll_cb" in one
… …
711 # use a low priority so other tasks have priority 1499 # use a low priority so other tasks have priority
712 Event->io (fd => IO::AIO::poll_fileno, 1500 Event->io (fd => IO::AIO::poll_fileno,
713 poll => 'r', nice => 1, 1501 poll => 'r', nice => 1,
714 cb => &IO::AIO::poll_cb); 1502 cb => &IO::AIO::poll_cb);
715 1503
716 IO::AIO::poll_wait
717 If there are any outstanding requests and none of them in the result
718 phase, wait till the result filehandle becomes ready for reading
719 (simply does a "select" on the filehandle. This is useful if you
720 want to synchronously wait for some requests to finish).
721
722 See "nreqs" for an example.
723
724 IO::AIO::poll
725 Waits until some requests have been handled.
726
727 Returns the number of requests processed, but is otherwise strictly
728 equivalent to:
729
730 IO::AIO::poll_wait, IO::AIO::poll_cb
731
732 IO::AIO::flush
733 Wait till all outstanding AIO requests have been handled.
734
735 Strictly equivalent to:
736
737 IO::AIO::poll_wait, IO::AIO::poll_cb
738 while IO::AIO::nreqs;
739
740 CONTROLLING THE NUMBER OF THREADS 1504 CONTROLLING THE NUMBER OF THREADS
741 IO::AIO::min_parallel $nthreads 1505 IO::AIO::min_parallel $nthreads
742 Set the minimum number of AIO threads to $nthreads. The current 1506 Set the minimum number of AIO threads to $nthreads. The current
743 default is 8, which means eight asynchronous operations can execute 1507 default is 8, which means eight asynchronous operations can execute
744 concurrently at any one time (the number of outstanding requests, 1508 concurrently at any one time (the number of outstanding requests,
… …
773 1537
774 Under normal circumstances you don't need to call this function. 1538 Under normal circumstances you don't need to call this function.
775 1539
776 IO::AIO::max_idle $nthreads 1540 IO::AIO::max_idle $nthreads
777 Limit the number of threads (default: 4) that are allowed to idle 1541 Limit the number of threads (default: 4) that are allowed to idle
778 (i.e., threads that did not get a request to process within 10 1542 (i.e., threads that did not get a request to process within the idle
779 seconds). That means if a thread becomes idle while $nthreads other 1543 timeout (default: 10 seconds). That means if a thread becomes idle
780 threads are also idle, it will free its resources and exit. 1544 while $nthreads other threads are also idle, it will free its
1545 resources and exit.
781 1546
782 This is useful when you allow a large number of threads (e.g. 100 or 1547 This is useful when you allow a large number of threads (e.g. 100 or
783 1000) to allow for extremely high load situations, but want to free 1548 1000) to allow for extremely high load situations, but want to free
784 resources under normal circumstances (1000 threads can easily 1549 resources under normal circumstances (1000 threads can easily
785 consume 30MB of RAM). 1550 consume 30MB of RAM).
786 1551
787 The default is probably ok in most situations, especially if thread 1552 The default is probably ok in most situations, especially if thread
788 creation is fast. If thread creation is very slow on your system you 1553 creation is fast. If thread creation is very slow on your system you
789 might want to use larger values. 1554 might want to use larger values.
790 1555
1556 IO::AIO::idle_timeout $seconds
1557 Sets the minimum idle timeout (default 10) after which worker
1558 threads are allowed to exit. SEe "IO::AIO::max_idle".
1559
791 $oldmaxreqs = IO::AIO::max_outstanding $maxreqs 1560 IO::AIO::max_outstanding $maxreqs
1561 Sets the maximum number of outstanding requests to $nreqs. If you do
1562 queue up more than this number of requests, the next call to
1563 "IO::AIO::poll_cb" (and other functions calling "poll_cb", such as
1564 "IO::AIO::flush" or "IO::AIO::poll") will block until the limit is
1565 no longer exceeded.
1566
1567 In other words, this setting does not enforce a queue limit, but can
1568 be used to make poll functions block if the limit is exceeded.
1569
792 This is a very bad function to use in interactive programs because 1570 This is a very bad function to use in interactive programs because
793 it blocks, and a bad way to reduce concurrency because it is 1571 it blocks, and a bad way to reduce concurrency because it is
794 inexact: Better use an "aio_group" together with a feed callback. 1572 inexact: Better use an "aio_group" together with a feed callback.
795 1573
796 Sets the maximum number of outstanding requests to $nreqs. If you to 1574 Its main use is in scripts without an event loop - when you want to
797 queue up more than this number of requests, the next call to the 1575 stat a lot of files, you can write something like this:
798 "poll_cb" (and "poll_some" and other functions calling "poll_cb")
799 function will block until the limit is no longer exceeded.
800 1576
801 The default value is very large, so there is no practical limit on 1577 IO::AIO::max_outstanding 32;
1578
1579 for my $path (...) {
1580 aio_stat $path , ...;
1581 IO::AIO::poll_cb;
1582 }
1583
1584 IO::AIO::flush;
1585
1586 The call to "poll_cb" inside the loop will normally return
1587 instantly, but as soon as more thna 32 reqeusts are in-flight, it
1588 will block until some requests have been handled. This keeps the
1589 loop from pushing a large number of "aio_stat" requests onto the
1590 queue.
1591
1592 The default value for "max_outstanding" is very large, so there is
802 the number of outstanding requests. 1593 no practical limit on the number of outstanding requests.
803
804 You can still queue as many requests as you want. Therefore,
805 "max_oustsanding" is mainly useful in simple scripts (with low
806 values) or as a stop gap to shield against fatal memory overflow
807 (with large values).
808 1594
809 STATISTICAL INFORMATION 1595 STATISTICAL INFORMATION
810 IO::AIO::nreqs 1596 IO::AIO::nreqs
811 Returns the number of requests currently in the ready, execute or 1597 Returns the number of requests currently in the ready, execute or
812 pending states (i.e. for which their callback has not been invoked 1598 pending states (i.e. for which their callback has not been invoked
… …
823 1609
824 IO::AIO::npending 1610 IO::AIO::npending
825 Returns the number of requests currently in the pending state 1611 Returns the number of requests currently in the pending state
826 (executed, but not yet processed by poll_cb). 1612 (executed, but not yet processed by poll_cb).
827 1613
1614 SUBSECOND STAT TIME ACCESS
1615 Both "aio_stat"/"aio_lstat" and perl's "stat"/"lstat" functions can
1616 generally find access/modification and change times with subsecond time
1617 accuracy of the system supports it, but perl's built-in functions only
1618 return the integer part.
1619
1620 The following functions return the timestamps of the most recent stat
1621 with subsecond precision on most systems and work both after
1622 "aio_stat"/"aio_lstat" and perl's "stat"/"lstat" calls. Their return
1623 value is only meaningful after a successful "stat"/"lstat" call, or
1624 during/after a successful "aio_stat"/"aio_lstat" callback.
1625
1626 This is similar to the Time::HiRes "stat" functions, but can return full
1627 resolution without rounding and work with standard perl "stat",
1628 alleviating the need to call the special "Time::HiRes" functions, which
1629 do not act like their perl counterparts.
1630
1631 On operating systems or file systems where subsecond time resolution is
1632 not supported or could not be detected, a fractional part of 0 is
1633 returned, so it is always safe to call these functions.
1634
1635 $seconds = IO::AIO::st_atime, IO::AIO::st_mtime, IO::AIO::st_ctime,
1636 IO::AIO::st_btime
1637 Return the access, modication, change or birth time, respectively,
1638 including fractional part. Due to the limited precision of floating
1639 point, the accuracy on most platforms is only a bit better than
1640 milliseconds for times around now - see the *nsec* function family,
1641 below, for full accuracy.
1642
1643 File birth time is only available when the OS and perl support it
1644 (on FreeBSD and NetBSD at the time of this writing, although support
1645 is adaptive, so if your OS/perl gains support, IO::AIO can take
1646 avdantage of it). On systems where it isn't available, 0 is
1647 currently returned, but this might change to "undef" in a future
1648 version.
1649
1650 ($atime, $mtime, $ctime, $btime, ...) = IO::AIO::st_xtime
1651 Returns access, modification, change and birth time all in one go,
1652 and maybe more times in the future version.
1653
1654 $nanoseconds = IO::AIO::st_atimensec, IO::AIO::st_mtimensec,
1655 IO::AIO::st_ctimensec, IO::AIO::st_btimensec
1656 Return the fractional access, modifcation, change or birth time, in
1657 nanoseconds, as an integer in the range 0 to 999999999.
1658
1659 Note that no accessors are provided for access, modification and
1660 change times - you need to get those from "stat _" if required ("int
1661 IO::AIO::st_atime" and so on will *not* generally give you the
1662 correct value).
1663
1664 $seconds = IO::AIO::st_btimesec
1665 The (integral) seconds part of the file birth time, if available.
1666
1667 ($atime, $mtime, $ctime, $btime, ...) = IO::AIO::st_xtimensec
1668 Like the functions above, but returns all four times in one go (and
1669 maybe more in future versions).
1670
1671 $counter = IO::AIO::st_gen
1672 Returns the generation counter (in practice this is just a random
1673 number) of the file. This is only available on platforms which have
1674 this member in their "struct stat" (most BSDs at the time of this
1675 writing) and generally only to the root usert. If unsupported, 0 is
1676 returned, but this might change to "undef" in a future version.
1677
1678 Example: print the high resolution modification time of /etc, using
1679 "stat", and "IO::AIO::aio_stat".
1680
1681 if (stat "/etc") {
1682 printf "stat(/etc) mtime: %f\n", IO::AIO::st_mtime;
1683 }
1684
1685 IO::AIO::aio_stat "/etc", sub {
1686 $_[0]
1687 and return;
1688
1689 printf "aio_stat(/etc) mtime: %d.%09d\n", (stat _)[9], IO::AIO::st_mtimensec;
1690 };
1691
1692 IO::AIO::flush;
1693
1694 Output of the awbove on my system, showing reduced and full accuracy:
1695
1696 stat(/etc) mtime: 1534043702.020808
1697 aio_stat(/etc) mtime: 1534043702.020807792
1698
1699 MISCELLANEOUS FUNCTIONS
1700 IO::AIO implements some functions that are useful when you want to use
1701 some "Advanced I/O" function not available to in Perl, without going the
1702 "Asynchronous I/O" route. Many of these have an asynchronous "aio_*"
1703 counterpart.
1704
1705 $numfd = IO::AIO::get_fdlimit
1706 This function is *EXPERIMENTAL* and subject to change.
1707
1708 Tries to find the current file descriptor limit and returns it, or
1709 "undef" and sets $! in case of an error. The limit is one larger
1710 than the highest valid file descriptor number.
1711
1712 IO::AIO::min_fdlimit [$numfd]
1713 This function is *EXPERIMENTAL* and subject to change.
1714
1715 Try to increase the current file descriptor limit(s) to at least
1716 $numfd by changing the soft or hard file descriptor resource limit.
1717 If $numfd is missing, it will try to set a very high limit, although
1718 this is not recommended when you know the actual minimum that you
1719 require.
1720
1721 If the limit cannot be raised enough, the function makes a
1722 best-effort attempt to increase the limit as much as possible, using
1723 various tricks, while still failing. You can query the resulting
1724 limit using "IO::AIO::get_fdlimit".
1725
1726 If an error occurs, returns "undef" and sets $!, otherwise returns
1727 true.
1728
1729 IO::AIO::sendfile $ofh, $ifh, $offset, $count
1730 Calls the "eio_sendfile_sync" function, which is like
1731 "aio_sendfile", but is blocking (this makes most sense if you know
1732 the input data is likely cached already and the output filehandle is
1733 set to non-blocking operations).
1734
1735 Returns the number of bytes copied, or -1 on error.
1736
1737 IO::AIO::fadvise $fh, $offset, $len, $advice
1738 Simply calls the "posix_fadvise" function (see its manpage for
1739 details). The following advice constants are available:
1740 "IO::AIO::FADV_NORMAL", "IO::AIO::FADV_SEQUENTIAL",
1741 "IO::AIO::FADV_RANDOM", "IO::AIO::FADV_NOREUSE",
1742 "IO::AIO::FADV_WILLNEED", "IO::AIO::FADV_DONTNEED".
1743
1744 On systems that do not implement "posix_fadvise", this function
1745 returns ENOSYS, otherwise the return value of "posix_fadvise".
1746
1747 IO::AIO::madvise $scalar, $offset, $len, $advice
1748 Simply calls the "posix_madvise" function (see its manpage for
1749 details). The following advice constants are available:
1750 "IO::AIO::MADV_NORMAL", "IO::AIO::MADV_SEQUENTIAL",
1751 "IO::AIO::MADV_RANDOM", "IO::AIO::MADV_WILLNEED",
1752 "IO::AIO::MADV_DONTNEED".
1753
1754 If $offset is negative, counts from the end. If $length is negative,
1755 the remaining length of the $scalar is used. If possible, $length
1756 will be reduced to fit into the $scalar.
1757
1758 On systems that do not implement "posix_madvise", this function
1759 returns ENOSYS, otherwise the return value of "posix_madvise".
1760
1761 IO::AIO::mprotect $scalar, $offset, $len, $protect
1762 Simply calls the "mprotect" function on the preferably AIO::mmap'ed
1763 $scalar (see its manpage for details). The following protect
1764 constants are available: "IO::AIO::PROT_NONE", "IO::AIO::PROT_READ",
1765 "IO::AIO::PROT_WRITE", "IO::AIO::PROT_EXEC".
1766
1767 If $offset is negative, counts from the end. If $length is negative,
1768 the remaining length of the $scalar is used. If possible, $length
1769 will be reduced to fit into the $scalar.
1770
1771 On systems that do not implement "mprotect", this function returns
1772 ENOSYS, otherwise the return value of "mprotect".
1773
1774 IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
1775 Memory-maps a file (or anonymous memory range) and attaches it to
1776 the given $scalar, which will act like a string scalar. Returns true
1777 on success, and false otherwise.
1778
1779 The scalar must exist, but its contents do not matter - this means
1780 you cannot use a nonexistant array or hash element. When in doubt,
1781 "undef" the scalar first.
1782
1783 The only operations allowed on the mmapped scalar are
1784 "substr"/"vec", which don't change the string length, and most
1785 read-only operations such as copying it or searching it with regexes
1786 and so on.
1787
1788 Anything else is unsafe and will, at best, result in memory leaks.
1789
1790 The memory map associated with the $scalar is automatically removed
1791 when the $scalar is undef'd or destroyed, or when the
1792 "IO::AIO::mmap" or "IO::AIO::munmap" functions are called on it.
1793
1794 This calls the "mmap"(2) function internally. See your system's
1795 manual page for details on the $length, $prot and $flags parameters.
1796
1797 The $length must be larger than zero and smaller than the actual
1798 filesize.
1799
1800 $prot is a combination of "IO::AIO::PROT_NONE",
1801 "IO::AIO::PROT_EXEC", "IO::AIO::PROT_READ" and/or
1802 "IO::AIO::PROT_WRITE",
1803
1804 $flags can be a combination of "IO::AIO::MAP_SHARED" or
1805 "IO::AIO::MAP_PRIVATE", or a number of system-specific flags (when
1806 not available, the are 0): "IO::AIO::MAP_ANONYMOUS" (which is set to
1807 "MAP_ANON" if your system only provides this constant),
1808 "IO::AIO::MAP_LOCKED", "IO::AIO::MAP_NORESERVE",
1809 "IO::AIO::MAP_POPULATE", "IO::AIO::MAP_NONBLOCK",
1810 "IO::AIO::MAP_FIXED", "IO::AIO::MAP_GROWSDOWN",
1811 "IO::AIO::MAP_32BIT", "IO::AIO::MAP_HUGETLB" or
1812 "IO::AIO::MAP_STACK".
1813
1814 If $fh is "undef", then a file descriptor of -1 is passed.
1815
1816 $offset is the offset from the start of the file - it generally must
1817 be a multiple of "IO::AIO::PAGESIZE" and defaults to 0.
1818
1819 Example:
1820
1821 use Digest::MD5;
1822 use IO::AIO;
1823
1824 open my $fh, "<verybigfile"
1825 or die "$!";
1826
1827 IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
1828 or die "verybigfile: $!";
1829
1830 my $fast_md5 = md5 $data;
1831
1832 IO::AIO::munmap $scalar
1833 Removes a previous mmap and undefines the $scalar.
1834
1835 IO::AIO::mremap $scalar, $new_length, $flags = MREMAP_MAYMOVE[,
1836 $new_address = 0]
1837 Calls the Linux-specific mremap(2) system call. The $scalar must
1838 have been mapped by "IO::AIO::mmap", and $flags must currently
1839 either be 0 or "IO::AIO::MREMAP_MAYMOVE".
1840
1841 Returns true if successful, and false otherwise. If the underlying
1842 mmapped region has changed address, then the true value has the
1843 numerical value 1, otherwise it has the numerical value 0:
1844
1845 my $success = IO::AIO::mremap $mmapped, 8192, IO::AIO::MREMAP_MAYMOVE
1846 or die "mremap: $!";
1847
1848 if ($success*1) {
1849 warn "scalar has chanegd address in memory\n";
1850 }
1851
1852 "IO::AIO::MREMAP_FIXED" and the $new_address argument are currently
1853 implemented, but not supported and might go away in a future
1854 version.
1855
1856 On systems where this call is not supported or is not emulated, this
1857 call returns falls and sets $! to "ENOSYS".
1858
1859 IO::AIO::mlockall $flags
1860 Calls the "eio_mlockall_sync" function, which is like
1861 "aio_mlockall", but is blocking.
1862
1863 IO::AIO::munlock $scalar, $offset = 0, $length = undef
1864 Calls the "munlock" function, undoing the effects of a previous
1865 "aio_mlock" call (see its description for details).
1866
1867 IO::AIO::munlockall
1868 Calls the "munlockall" function.
1869
1870 On systems that do not implement "munlockall", this function returns
1871 ENOSYS, otherwise the return value of "munlockall".
1872
1873 IO::AIO::splice $r_fh, $r_off, $w_fh, $w_off, $length, $flags
1874 Calls the GNU/Linux splice(2) syscall, if available. If $r_off or
1875 $w_off are "undef", then "NULL" is passed for these, otherwise they
1876 should be the file offset.
1877
1878 $r_fh and $w_fh should not refer to the same file, as splice might
1879 silently corrupt the data in this case.
1880
1881 The following symbol flag values are available:
1882 "IO::AIO::SPLICE_F_MOVE", "IO::AIO::SPLICE_F_NONBLOCK",
1883 "IO::AIO::SPLICE_F_MORE" and "IO::AIO::SPLICE_F_GIFT".
1884
1885 See the splice(2) manpage for details.
1886
1887 IO::AIO::tee $r_fh, $w_fh, $length, $flags
1888 Calls the GNU/Linux tee(2) syscall, see its manpage and the
1889 description for "IO::AIO::splice" above for details.
1890
1891 $actual_size = IO::AIO::pipesize $r_fh[, $new_size]
1892 Attempts to query or change the pipe buffer size. Obviously works
1893 only on pipes, and currently works only on GNU/Linux systems, and
1894 fails with -1/"ENOSYS" everywhere else. If anybody knows how to
1895 influence pipe buffer size on other systems, drop me a note.
1896
1897 ($rfh, $wfh) = IO::AIO::pipe2 [$flags]
1898 This is a direct interface to the Linux pipe2(2) system call. If
1899 $flags is missing or 0, then this should be the same as a call to
1900 perl's built-in "pipe" function and create a new pipe, and works on
1901 systems that lack the pipe2 syscall. On win32, this case invokes
1902 "_pipe (..., 4096, O_BINARY)".
1903
1904 If $flags is non-zero, it tries to invoke the pipe2 system call with
1905 the given flags (Linux 2.6.27, glibc 2.9).
1906
1907 On success, the read and write file handles are returned.
1908
1909 On error, nothing will be returned. If the pipe2 syscall is missing
1910 and $flags is non-zero, fails with "ENOSYS".
1911
1912 Please refer to pipe2(2) for more info on the $flags, but at the
1913 time of this writing, "IO::AIO::O_CLOEXEC", "IO::AIO::O_NONBLOCK"
1914 and "IO::AIO::O_DIRECT" (Linux 3.4, for packet-based pipes) were
1915 supported.
1916
1917 Example: create a pipe race-free w.r.t. threads and fork:
1918
1919 my ($rfh, $wfh) = IO::AIO::pipe2 IO::AIO::O_CLOEXEC
1920 or die "pipe2: $!\n";
1921
1922 $fh = IO::AIO::eventfd [$initval, [$flags]]
1923 This is a direct interface to the Linux eventfd(2) system call. The
1924 (unhelpful) defaults for $initval and $flags are 0 for both.
1925
1926 On success, the new eventfd filehandle is returned, otherwise
1927 returns "undef". If the eventfd syscall is missing, fails with
1928 "ENOSYS".
1929
1930 Please refer to eventfd(2) for more info on this call.
1931
1932 The following symbol flag values are available:
1933 "IO::AIO::EFD_CLOEXEC", "IO::AIO::EFD_NONBLOCK" and
1934 "IO::AIO::EFD_SEMAPHORE" (Linux 2.6.30).
1935
1936 Example: create a new eventfd filehandle:
1937
1938 $fh = IO::AIO::eventfd 0, IO::AIO::O_CLOEXEC
1939 or die "eventfd: $!\n";
1940
1941 $fh = IO::AIO::timerfd_create $clockid[, $flags]
1942 This is a direct interface to the Linux timerfd_create(2) system
1943 call. The (unhelpful) default for $flags is 0.
1944
1945 On success, the new timerfd filehandle is returned, otherwise
1946 returns "undef". If the eventfd syscall is missing, fails with
1947 "ENOSYS".
1948
1949 Please refer to timerfd_create(2) for more info on this call.
1950
1951 The following $clockid values are available:
1952 "IO::AIO::CLOCK_REALTIME", "IO::AIO::CLOCK_MONOTONIC"
1953 "IO::AIO::CLOCK_CLOCK_BOOTTIME" (Linux 3.15)
1954 "IO::AIO::CLOCK_CLOCK_REALTIME_ALARM" (Linux 3.11) and
1955 "IO::AIO::CLOCK_CLOCK_BOOTTIME_ALARM" (Linux 3.11).
1956
1957 The following $flags values are available (Linux 2.6.27):
1958 "IO::AIO::TFD_NONBLOCK" and "IO::AIO::TFD_CLOEXEC".
1959
1960 Example: create a new timerfd and set it to one-second repeated
1961 alarms, then wait for two alarms:
1962
1963 my $fh = IO::AIO::timerfd_create IO::AIO::CLOCK_BOOTTIME, IO::AIO::TFD_CLOEXEC
1964 or die "timerfd_create: $!\n";
1965
1966 defined IO::AIO::timerfd_settime $fh, 0, 1, 1
1967 or die "timerfd_settime: $!\n";
1968
1969 for (1..2) {
1970 8 == sysread $fh, my $buf, 8
1971 or die "timerfd read failure\n";
1972
1973 printf "number of expirations (likely 1): %d\n",
1974 unpack "Q", $buf;
1975 }
1976
1977 ($cur_interval, $cur_value) = IO::AIO::timerfd_settime $fh, $flags,
1978 $new_interval, $nbw_value
1979 This is a direct interface to the Linux timerfd_settime(2) system
1980 call. Please refer to its manpage for more info on this call.
1981
1982 The new itimerspec is specified using two (possibly fractional)
1983 second values, $new_interval and $new_value).
1984
1985 On success, the current interval and value are returned (as per
1986 "timerfd_gettime"). On failure, the empty list is returned.
1987
1988 The following $flags values are available:
1989 "IO::AIO::TFD_TIMER_ABSTIME" and "IO::AIO::TFD_TIMER_CANCEL_ON_SET".
1990
1991 See "IO::AIO::timerfd_create" for a full example.
1992
1993 ($cur_interval, $cur_value) = IO::AIO::timerfd_gettime $fh
1994 This is a direct interface to the Linux timerfd_gettime(2) system
1995 call. Please refer to its manpage for more info on this call.
1996
1997 On success, returns the current values of interval and value for the
1998 given timerfd (as potentially fractional second values). On failure,
1999 the empty list is returned.
2000
2001EVENT LOOP INTEGRATION
2002 It is recommended to use AnyEvent::AIO to integrate IO::AIO
2003 automatically into many event loops:
2004
2005 # AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
2006 use AnyEvent::AIO;
2007
2008 You can also integrate IO::AIO manually into many event loops, here are
2009 some examples of how to do this:
2010
2011 # EV integration
2012 my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
2013
2014 # Event integration
2015 Event->io (fd => IO::AIO::poll_fileno,
2016 poll => 'r',
2017 cb => \&IO::AIO::poll_cb);
2018
2019 # Glib/Gtk2 integration
2020 add_watch Glib::IO IO::AIO::poll_fileno,
2021 in => sub { IO::AIO::poll_cb; 1 };
2022
2023 # Tk integration
2024 Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
2025 readable => \&IO::AIO::poll_cb);
2026
2027 # Danga::Socket integration
2028 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
2029 \&IO::AIO::poll_cb);
2030
828 FORK BEHAVIOUR 2031 FORK BEHAVIOUR
829 This module should do "the right thing" when the process using it forks: 2032 Usage of pthreads in a program changes the semantics of fork
2033 considerably. Specifically, only async-safe functions can be called
2034 after fork. Perl doesn't know about this, so in general, you cannot call
2035 fork with defined behaviour in perl if pthreads are involved. IO::AIO
2036 uses pthreads, so this applies, but many other extensions and (for
2037 inexplicable reasons) perl itself often is linked against pthreads, so
2038 this limitation applies to quite a lot of perls.
830 2039
831 Before the fork, IO::AIO enters a quiescent state where no requests can 2040 This module no longer tries to fight your OS, or POSIX. That means
832 be added in other threads and no results will be processed. After the 2041 IO::AIO only works in the process that loaded it. Forking is fully
833 fork the parent simply leaves the quiescent state and continues 2042 supported, but using IO::AIO in the child is not.
834 request/result processing, while the child frees the request/result
835 queue (so that the requests started before the fork will only be handled
836 in the parent). Threads will be started on demand until the limit set in
837 the parent process has been reached again.
838 2043
839 In short: the parent will, after a short pause, continue as if fork had 2044 You might get around by not *using* IO::AIO before (or after) forking.
840 not been called, while the child will act as if IO::AIO has not been 2045 You could also try to call the IO::AIO::reinit function in the child:
841 used yet. 2046
2047 IO::AIO::reinit
2048 Abandons all current requests and I/O threads and simply
2049 reinitialises all data structures. This is not an operation
2050 supported by any standards, but happens to work on GNU/Linux and
2051 some newer BSD systems.
2052
2053 The only reasonable use for this function is to call it after
2054 forking, if "IO::AIO" was used in the parent. Calling it while
2055 IO::AIO is active in the process will result in undefined behaviour.
2056 Calling it at any time will also result in any undefined (by POSIX)
2057 behaviour.
2058
2059 LINUX-SPECIFIC CALLS
2060 When a call is documented as "linux-specific" then this means it
2061 originated on GNU/Linux. "IO::AIO" will usually try to autodetect the
2062 availability and compatibility of such calls regardless of the platform
2063 it is compiled on, so platforms such as FreeBSD which often implement
2064 these calls will work. When in doubt, call them and see if they fail wth
2065 "ENOSYS".
842 2066
843 MEMORY USAGE 2067 MEMORY USAGE
844 Per-request usage: 2068 Per-request usage:
845 2069
846 Each aio request uses - depending on your architecture - around 100-200 2070 Each aio request uses - depending on your architecture - around 100-200
847 bytes of memory. In addition, stat requests need a stat buffer (possibly 2071 bytes of memory. In addition, stat requests need a stat buffer (possibly
848 a few hundred bytes), readdir requires a result buffer and so on. Perl 2072 a few hundred bytes), readdir requires a result buffer and so on. Perl
849 scalars and other data passed into aio requests will also be locked and 2073 scalars and other data passed into aio requests will also be locked and
850 will consume memory till the request has entered the done state. 2074 will consume memory till the request has entered the done state.
851 2075
852 This is now awfully much, so queuing lots of requests is not usually a 2076 This is not awfully much, so queuing lots of requests is not usually a
853 problem. 2077 problem.
854 2078
855 Per-thread usage: 2079 Per-thread usage:
856 2080
857 In the execution phase, some aio requests require more memory for 2081 In the execution phase, some aio requests require more memory for
858 temporary buffers, and each thread requires a stack and other data 2082 temporary buffers, and each thread requires a stack and other data
859 structures (usually around 16k-128k, depending on the OS). 2083 structures (usually around 16k-128k, depending on the OS).
860 2084
861KNOWN BUGS 2085KNOWN BUGS
862 Known bugs will be fixed in the next release. 2086 Known bugs will be fixed in the next release :)
2087
2088KNOWN ISSUES
2089 Calls that try to "import" foreign memory areas (such as "IO::AIO::mmap"
2090 or "IO::AIO::aio_slurp") do not work with generic lvalues, such as
2091 non-created hash slots or other scalars I didn't think of. It's best to
2092 avoid such and either use scalar variables or making sure that the
2093 scalar exists (e.g. by storing "undef") and isn't "funny" (e.g. tied).
2094
2095 I am not sure anything can be done about this, so this is considered a
2096 known issue, rather than a bug.
863 2097
864SEE ALSO 2098SEE ALSO
865 Coro::AIO. 2099 AnyEvent::AIO for easy integration into event loops, Coro::AIO for a
2100 more natural syntax.
866 2101
867AUTHOR 2102AUTHOR
868 Marc Lehmann <schmorp@schmorp.de> 2103 Marc Lehmann <schmorp@schmorp.de>
869 http://home.schmorp.de/ 2104 http://home.schmorp.de/
870 2105

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